The first textbooks ____ for teaching English as a foreign language came out in the 16th century.(NMET94 34)A.having written B.to be written C.being written D.written为什么选D?

问题描述:

The first textbooks ____ for teaching English as a foreign language came out in the 16th century.(NMET94 34)
A.having written B.to be written C.being written D.written
为什么选D?

D.=the first textbooks (which are)written for...
省略了从句的主谓