Fertile soil has lots of humus. Why?

$(a)$ How is soil pollution caused?
$(b)$ Write three ways to prevent soil pollution.

Why is step farming common in hills?

Which type of soil is more likely to be removed very quickly?

The endoskeletons and exoskeletons of various animals are also formed from:

Sehaj tried to set up a small kitchen garden in his backyard. However,the soil was sandy and unsuitable for growing vegetables. Within seven days,he solved the problem and started planting seedlings.
$(a)$ Why was the soil in Sehaj's backyard unsuitable for growing vegetables?
$(b)$ What could be the solution he found? Mention any two.