---Why do you look so upset?---There are so many troublesome problems .A. remaining to be

问题补充：

---Why do you look so upset?

---There are so many troublesome problems .

A. remaining to be settled

B. remained settled

C. remaining to settle

D. remained to be settled

答案：

(答案→)A. remaining to be settled

B. remained settled

C. remaining to settle

D. remained to be settled

解析：考察非谓语动词。根据句子结构可知，该处为problems的定语，remain是系动词，无被动。故排除BD. Remain的用法是sth remain to be done，

句意为，有很多麻烦的问题留待解决。