—Why do you eat so little?—I’m a diet to reduce some weight.A. inB. onC. withD. under

问题补充：

—Why do you eat so little?

—I’m a diet to reduce some weight.

A. in

B. on

C. with

D. under

答案：

A. in

(答案→)B. on

C. with

D. under

解析：考查固定搭配。Be on a diet在节食。选B。