Test: Human Body and Health - Class 6 MCQ

Vitamin K is known as the "clot master" because it plays a crucial role in blood clotting.

• Vitamin K helps in the synthesis of proteins that are involved in blood coagulation, thus preventing excessive bleeding.
• The other vitamins listed do not have a direct role in blood clotting:
  • Vitamin A (Option A) is important for vision, immune function, and skin health.
  • Vitamin B (Option B) refers to a group of vitamins that are important for energy production, nerve function, and cell metabolism.
  • Vitamin D (Option D) is essential for calcium absorption and bone health.

Thus, the correct answer is Option C (Vitamin K).

Orange is the best choice for helping heal a wound.

• Oranges are rich in Vitamin C, which plays a vital role in collagen formation and tissue repair. Vitamin C helps the body heal wounds by supporting the immune system and promoting the healing of damaged skin and tissues.

• Bananas (Option A) are nutritious but do not have a significant role in wound healing compared to oranges.

• Apples (Option B) are healthy and provide fiber, but they don't have a direct impact on wound healing like Vitamin C-rich fruits.

Thus, the correct answer is Option C (Orange).

Vitamin C is known for boosting the immune system and helping the body fight infections.

• Vitamin C enhances the immune system by stimulating the production and function of white blood cells, which play a key role in fighting infections. It also acts as an antioxidant.
• Vitamin A (Option A) supports vision and immune function but is not as directly involved in fighting infections.
• Vitamin B (Option B) refers to a group of vitamins important for energy production and metabolism.
• Vitamin D (Option D) helps in calcium absorption and bone health, and also plays a role in immune function, but Vitamin C is more directly linked to boosting immunity.

Thus, the correct answer is Option C (Vitamin C).

Skin has the highest rate of regeneration among the listed tissues.

• Skin is constantly exposed to wear and tear, and it has a remarkable ability to regenerate quickly. It heals fast after minor injuries or cuts.
• Kidney tissues (Option A), Muscles (Option B), and Brain (Option D) have limited regenerative abilities. For instance, muscle tissue can regenerate to some extent, but not as quickly as skin. The brain has very limited regenerative capacity and is one of the slowest to heal.

Thus, the correct answer is Option C (Skin).

The part of the tooth visible above the gum is called the crown.

• Crown is the portion of the tooth that is visible and exposed above the gum line. It is covered by enamel and is the part that comes into contact with food.
• Root (Option A) is the part of the tooth that is embedded in the gum and holds the tooth in place.
• Cavity (Option B) refers to the decay or hole that can form in the tooth due to bacterial activity.
• Plaque (Option D) is a sticky film of bacteria that forms on teeth, often leading to tooth decay and gum disease.

Thus, the correct answer is Option C (Crown).

Light inhibits the production of melatonin.

• Melatonin is a hormone that regulates the sleep-wake cycle, or circadian rhythm. It is produced by the pineal gland, and its secretion is controlled by the amount of light exposure. Exposure to light, especially blue light from screens or sunlight, inhibits melatonin production, making it harder to fall asleep.
• Drugs (Option A) and Alcohol (Option B) can also affect melatonin levels, but light is the primary factor that inhibits its production.
• Darren (Option D) is not related to melatonin or circadian rhythms.

Thus, the correct answer is Option C (Light).

Teeth help you talk (speak).

• Teeth are essential for articulation, as they help in forming sounds and words when we speak.
• Taste (Option A) is primarily the function of the taste buds on the tongue.
• Hear (Option C) is related to the ear and auditory system, not teeth.
• Think (Option D) is related to the brain, not teeth.

Thus, the correct answer is Option B (Talk).

The iris is the structure responsible for controlling the diameter and size of the pupil and also determines the color of the eye.

• The iris is the colored part of the eye. It contains muscles that regulate the size of the pupil, controlling the amount of light entering the eye.
• Cornea (Option A) is the transparent outer layer of the eye, which helps focus light but does not control pupil size or eye color.
• Pupil (Option B) is the opening in the center of the iris that allows light to enter the eye but is not responsible for controlling its size.
• Retina (Option D) is the light-sensitive layer at the back of the eye that detects light and sends signals to the brain, but it does not control the pupil or eye color.

Thus, the correct answer is Option C (Iris).

Sphincters are ring-like muscles that control the opening and closing of various passageways in the body.

• Stomach (Option A) contains sphincters at both ends: the lower esophageal sphincter (at the entrance of the stomach) and the pyloric sphincter (at the exit of the stomach). These muscles help regulate the flow of food and prevent reflux.
• The Mouth (Option B), Eye (Option C), and Ear (Option D) do not contain sphincters. While the eye has muscles like the orbicularis oculi (which closes the eyelid), they are not sphincters.

Thus, the correct answer is Option A (Stomach).

Blue eyes occur when there is comparatively little pigment (melanin) in the iris.

• The color of our eyes is determined by the amount and type of pigment in the iris. People with less melanin tend to have blue eyes, while those with more melanin have brown eyes. Green eyes have an intermediate amount of melanin.
• Hard (Option D) is not a valid eye color.

Thus, the correct answer is Option A (Blue).