The form in and returned within three weeks.A. is to be filledB. will fillC. is to fillD.

问题补充：

The form in and returned within three weeks.

A. is to be filled

B. will fill

C. is to fill

D. are going to be filled

答案：

(答案→)A. is to be filled

B. will fill

C. is to fill

D. are going to be filled

解析：时间状语within three weeks，表示将来的一段时间。be to表示将来一段时间内必定要进行的动作，而be going to表示“打算做某事”，故排除D，同时不定式的逻辑主语是form，动词形式用被动，排除B和C，故选A。