When instructors are interested in grading all answers to a specific question in a quiz they may opt to do the following:
From your course page, click into the quiz activity, scroll down and look to the left under Quiz Administration, expand the Results folder.
Choose Manual Grading, which then brings to a view that show which questions are left to be graded.
You can click on each question and view the student responses & grade/feedback to each of those responses.
Also note: the link to the Results folder appears in the footer of the Moodle screen when you are in the Results area. Scroll down to locate: