23. Ideally, the professional career diplomat should help in the ongoing maintenance of an effective American foreign policy despite changes in administration.
(A) in the ongoing maintenance of
(B) in the maintaining of
(C) maintain
(D) to maintain and continue（C）
(E) the maintenance of
是TO 省略了吗？其他HELP 的用法请指教！
谢谢！ | 
