The road isdesigned for only motor vehicles, so once ________, bicycles are not allowed togo along i

The road isdesigned for only motor vehicles, so once ________, bicycles are not allowed togo along it.

A.opens

B.havingopened

C.opening

D.opened

答案及解析： D

解析：

road与open之间是动宾关系，插入语用过去分词，表被动。