问题补充：
When I got back home I saw a message pinned to the door, “Sorry to miss you; will call later.”
A. read
B. reads
C. to read
D. reading
答案：
A. read
B. reads
C. to read
(答案→)D. reading
解析：考查本句中read与saw是同时进行，I与read之间构成主动关系，故用现在分词作伴随状语。句意，当我回到家时，我看到贴着一张字条，上面写着“抱歉很想你，稍后打电话。”
