How to estimate the time needed to read a question?

I have to prepare an online survey. Most of the questions will be along the line of:

Which of the following sentences exists in 'X' book?

A

B

C

D

I would like to limit cheating as much as possible. Since the survey is conducted online, I can't have any type of physical restrictions for the users who answer the question.

My main concern is that many people will use a search engine to see which of the four answers exist in the book.

In order to prevent that, I would like to set a time restriction for answering the questions. But the problem is that users may have different reading speeds they may miss some or all of the information in a question.

How can I balance between providing enough time to read a question and restricting the time to prevent cheating?