Today, people are paying more and more attention to their health,         books on keeping healthy extremely hot.

A．to make

B．making

C．make

D．made

把2a=3b改完成比例，正确的是（　　）

A．a：b=2：3

B．a：b=3：2

C．b：a=3：2

D．2：a=3：b