题目内容：

The dog,_____,will be made a good watchdog.
A.to train properly B.being trained properly C.properly to train D.trained properly
解析是（ 过去分词短语作条件状语,相当于if it is trained properly.

优质解答

这句话要表达的意思是
“如果狗被适当的训练了”即“if it is trained properly”,
trained properly在这里相当于“if it is trained properly”
过去分词短语有这样的用法 过去分词=if it is+ 过去分词