可以。which指伍察丛代的先没知行词是物，可以是腔樱单数，也可以是复数。如：
She gave me a book, which is expensive.
She gave me some books, which are bought from a nearby bookshop.
which指代的先行词也可能是前面整个一个句子，这时which后面的谓语动词只能用单数。如：
She got an A in the exam, which was due to her diligence.
.
这个问题好像存在好久了，说下自己的看法吧。 仅供参考。
which在非限制性定语从句中，用来指主句内容。
He made noise in class, which made his teacher angry.
这个句子其实= He made noise in class and it/ that made his teacher angry.
显然it或that, 应该指上文发生的返氏事情，或上文的情况。这里表现的比较含糊，没有数量之分，所以我觉得which后面不能用复数谓语动词。
上面山世派一个句子改成：He often makes noise and sleeps in class, which makes his teacher angry.
这里我觉得还是用单数谓语动词。
改逗贺成He often makes noise and sleeps in class and it/that makes his teacher angry.
不能说He often makes noise and sleeps in class and they/those make his teacher angry.
显得不伦不类。
By playing basketball, we can learn how to coordinate and can make a lot of friends, which is what we need/require.
I bought a lot of books, which are what I need most.