Question

It is important to ___________of a difficult chapter. a. Memorize c. Summarize b. Read to the end d. None of these

Answer 1

The answer is b. "read to the end"
It makes intuitive sense and is the only solution that is correct in terms of the grammar. 

Answer 2

The correct answer is option b. "Read to the end". In order to really understand a difficult chapter, it is important to not skip any section of the chapter, and it is important to read it to the end. Most of the time difficult chapters contain a lot of information and it is important to read all the content in order to completely understand it.