[求助]大全d-18

The National Labor Relations Act expressly forbids unions from engaging in secondary boycotts against companies not directly involved in a labor dispute.

(A) unions from engaging in

(B) the engagement by unions of

(C) unions to engage in

(D) unions from becoming engaged with（C）

(E) that unions engage upon

請教一下

字典裡forbid...from Ving跟forbid...to+V兩個都對啊

這裡為什麼只能選C呢

謝謝大家喔