Depending on the subject, he could go to his text book, online ebook, etc. He could look at his review if he was given one. He could find other books relating to the subject that could potentially help. (Not much to go on, hope this helps c:)
The correct answer is letter (B)The <span>laburnum’s</span> (trembling) branches can hardly bear the burden of the beauty of “the honey-sweet and honey-colored blossoms of a laburnum” (6–7), the subject to which <span>“theirs” refers.</span>
