_____ the front door _____, he had to enter the room through the back door. A．Seen; painted ..

_____ the front door _____, he had to enter the room through the back door. A．Seen; painted ..

D

see 表示的动作与句子谓语动词（had to enter）所表示的动作几乎同时发生，且与其逻辑主语（he）为主动关系，故用一般式。由句意“看到前门正在被漆，……”可知，第二空应用being painted。