【单选题】

In the 3rd paragraph, "... in the regions where it could be practiceD、.. ", here, "it" refers to______.

A、increaseC、agriculture
B、number D、species
A．

In the 3rd paragraph, "... in the regions where it could be practiceD、.. ", here, "it" refers to______.

B．increase
C．number
D．agriculture
E．species