To solve the traffic problem more and more bridges across the river every year. A. were

问题补充：

To solve the traffic problem, more and more bridges across the river every year.

A. were built

B. will build

C. are built

D. are building

答案：

A. were built

(答案→)B. will build

C. are built

D. are building

解析：句意：为了解决交通问题，每年河上建上了越来越多的桥。每年桥是被建造的，所以要用一般现在时态的被动语态。故选B。