The correct answer is option 'B' - ganja and charas affect the cardiovascular system.

Ganja and charas, commonly known as marijuana or cannabis, are drugs derived from the Cannabis plant. These drugs have psychoactive properties and can cause various effects on the body, including those on the cardiovascular system.

Here is a detailed explanation of how ganja and charas affect the cardiovascular system:

1. Vasodilation:
- Both ganja and charas contain cannabinoids, primarily tetrahydrocannabinol (THC), which can cause vasodilation.
- Vasodilation refers to the widening of blood vessels, leading to an increase in their diameter.
- When blood vessels dilate, it reduces peripheral resistance and allows for increased blood flow.
- This effect can cause a decrease in blood pressure.

2. Tachycardia:
- Another effect of ganja and charas on the cardiovascular system is an increase in heart rate, known as tachycardia.
- THC activates the sympathetic nervous system, which increases the release of norepinephrine and epinephrine, leading to an increased heart rate.
- Tachycardia can put additional stress on the heart and may have adverse effects, especially in individuals with pre-existing cardiovascular conditions.

3. Increased risk of heart attack:
- The combination of vasodilation and tachycardia can increase the risk of a heart attack, particularly in susceptible individuals.
- When blood vessels dilate, it can lead to a decrease in coronary blood flow, which may be insufficient to meet the increased oxygen demand due to tachycardia.
- This can result in myocardial ischemia, where the heart muscle does not receive enough oxygen, potentially leading to a heart attack.

4. Blood clotting:
- Ganja and charas can also affect blood clotting.
- THC has been shown to inhibit platelet aggregation, which is the process of platelets clumping together to form a blood clot.
- This effect may increase the risk of bleeding in individuals taking anticoagulant medications or those with bleeding disorders.

In summary, ganja and charas affect the cardiovascular system primarily through vasodilation, tachycardia, increased risk of heart attack, and alterations in blood clotting. It is important to note that these effects may vary depending on the dosage, frequency of use, and individual susceptibility.