Read the following passage and mark the letter A, B, C, or D to indicate the correct answer that best fits each of the numbered blanks.

Tests and exams are part of our school life. They have an important role (21) ____________ students' learning and education. Preparing for exams is a skill and not every student knows (22) ____________ to do it. Many students think that the easiest way is to learn everything by heart, but this isn't always the case. Knowledge is (23) ____________ more than remembering facts - it also involves understanding the information you learn. When you study for an exam, try to understand everything. Also, (24) ____________ attention to details. Another mistake that students make is listening to music and chatting on Facebook while they're learning. This does not (25) ____________ concentration!

They have an important role (21) ____________ students' learning and education.