The inner lining of the stomach is protected from hydrochloric acid by which of the following? Choose the correct one.

How do desert plants perform the photosynthesis process even though their stomata remain closed during the daytime?

Explain the importance of soil for plant growth.

In each of the following situations,what happens to the rate of photosynthesis?
$(a)$ Cloudy days
$(b)$ No rainfall in the area
$(c)$ Good manuring in the area
$(d)$ Stomata get blocked due to dust

$(a)$ What is the nature of food coming from the stomach?
$(b)$ Mention any two structural modifications in the small intestine which help in the absorption of food.

Why do veins have thin walls as compared to arteries?