这个涉及语法的学习。直接提问是Whose pen is it?类似的例如Who are you? What can you do?通俗点说,如果不是直接提问,而是接到另一句话,例如:我不知道你是谁。I don't Know who you are.这时候就改变顺序了,are you 变you are。同理:他问你你会做什么:He asks you what you can do(can you 变you can主语在前)。类似中文的“转述句”,英语里面叫“宾语从句”