Washing soda is used as detergent...it is also called as sodium carbonate... hence correct answer is A.

Answer:

Introduction:
Detergent powders are commonly used for washing clothes and other household items. They are made up of various chemicals, including salts, which help in the cleaning process. One of the salts commonly used in making detergent powder is washing soda.

Explanation:

1. Washing Soda:
Washing soda, also known as sodium carbonate (Na2CO3), is a salt that is commonly used in the production of detergent powders. It is a white, crystalline solid that is highly soluble in water. Washing soda has a high alkalinity and is known for its ability to remove tough stains and dirt from clothes.

2. Alkalinity:
The alkalinity of washing soda makes it an effective cleaning agent. It helps to neutralize the acidic components of stains and dirt, allowing them to be easily washed away. This property of washing soda makes it suitable for use in detergent powders.

3. Cleaning Action:
When washing soda is added to water, it dissociates into sodium ions (Na+) and carbonate ions (CO3^2-). These ions help in breaking down the dirt and stains by forming complexes with the fatty acids and oils present in them. This process is known as saponification.

4. pH Adjustment:
Washing soda also helps in adjusting the pH of the water. It increases the alkalinity of the water, which enhances the cleaning action of the detergent powder. The high pH of washing soda helps in breaking down the dirt and stains effectively.

5. Other Salts:
While washing soda is commonly used in making detergent powders, other salts such as sodium bicarbonate (baking soda) and common salt (sodium chloride) may also be used in smaller quantities. These salts contribute to the overall cleaning action and performance of the detergent powder.

Conclusion:
In conclusion, washing soda is the salt that is commonly used in making detergent powders. Its high alkalinity, ability to adjust pH, and effective cleaning action make it an ideal ingredient for removing tough stains and dirt from clothes.