Question

Organic food is the fastest-growing sector of US agriculture

Answer 1

Organic food indeed is one of the fastest-growing sectors of US agriculture. The reason for this is that people prefer to eat food which has not been particularly tampered with as far as chemicals go and would like to eat different goods in their natural state. 

Answer 2

Organic food is the fastest-growing sector of US agriculture - true.
As more people realize that processed food is unhealthy and dangerous, they begin to buy organic foods because they are natural, safe, and healthy.