______ horse is _______useful animal while tigers are dangerous ones.
问题描述：
______ horse is _______useful animal while tigers are dangerous ones.
A./ ,an B An ,a C.the ,an D a,a
答
D你看一下二楼的答案，能跟我解释一下吗~~这个可以用排除法horse和 useful如果用不定冠词的话，都必须用a