Foreigners often make some strange mistakes in Chinese when they study the most difficult language--- ---Chinese. We try to analyze typical sentences to correct these errors.

                Zuótiān nǐ zuò shénme le?
False: A: 昨天你做什么了?
             Zuótiān wǒ zuò kànshū le.
         B: 昨天我做看书了。
            Zuótiān nǐ zuò shénme le?
True: A: 昨天你做什么了?
            Zuótiān wǒ kànshū le.
         B: 昨天我看书了。

“做什么”是动宾词组,用来咨询进行的活动。在含有“做什么”的疑问句里,疑点应当是“做什么”,答案“看书”便是疑问所在。如果疑点仅仅是“什么”,答案自然写成了“做看书”,这是错的。
做什么 is a verb-object phrase which inquires about an activity. In an interrogative sentence containing 做什么, the question lies in 做什么 as a whole, to which the answer is 做看书. If the question is considered to lie 什么 alone, the answer naturally turns to be 做看书, which is definitely ungrammatical.