Chọn dạng động từ phù hợp trong câu tiếng Anh

Làm hộ em 2 câu này với ạ
1. The building of the bridge had been delayed for three years because of polirical problems on both sides of the rivers. Finally, it_____because the public demand action, and now many hours of driving have been saved for daily commuters
A. Was constructed
B. Get constructed
C. Constructed
D. Has constructed
2. My car made strange noise, sputtered to a stop,and then wouldn’t start again. Fortunately, the mechanic at my garage_____ the cause of the problem
A. Was discovering
B. Discovered
C.has been discovered
D. Was discovered