问题描述：
my brother was in his room ,______ in his experiment.
a:absorb b:to absorb
c:absorbing d:absorbed
请问选哪一个答案,为什么?
a:absorb b:to absorb
c:absorbing d:absorbed
请问选哪一个答案,为什么?
问题解答：
我来补答展开全文阅读