Find the mistake among the underlined words or phrases
Find the mistake: If (A) you do not understand (B) what were written (C) in the book, you could ask (D) Mr. Pike.
Knowledge: Words to ask
After the pronoun “what” (when being the subject), the verb is always in the 3rd person singular.
Edit: were written => was written
If you don’t understand what was written in the book, you could ask Mr. Pike.
If you don’t understand what is written in the book, you can ask Mr. Pike.
The answer to choose is: