根据下列内容，回答181-185题。
Anne Whitney, a sophomore at Colorado State University, first had a problem taking testswhen she began college. "I was always well prepared for my tests. Sometimes I studied for weeksbefore a test. Yet I would go in to take the test, only to find I could not answer the questions cot-rectly. I would blank out because of nervousness and fear. I couldn't think of the answer. My lowgrades on the tests did not show what I knew to the teacher." Another student in biology had simi-lar experiences. He said:"My first chemistry test was very difficult. Then, on the second test, I satdown to take it, and I was so nervous that I was shaking. My hands were moving up and down soquickly that it was hard to hold my pencil. I knew the material and I knew the answers. Yet !
couldn't even write them down! "
These two young students were experiencing something called test anxiety. Because a studentworries and is uneasy about a test, his or her mind does not work as well as it usually does. Thestudent cannot write or think clearly because of the extreme tension and nervousness. Althoughpoor grades are often a result of poor study habits, sometimes test anxiety causes the low grades.Recently, test anxiety has been recognized as a real problem, not just an excuse or a false expla-nation of lazy students.
Special university advising courses try to help students. In these courses, advisors try to helpstudents by teaching them how to manage test anxiety. At some universities, students take tests tomeasure their anxiety. If the tests show their anxiety is high, the students can take short courses tohelp them deal with their tensions. These courses teach students how to relax their bodies. Studentsare trained to become calm in very tense situations. By controlling their nervousness, they can lettheir minds work at ease. Learned information then comes out without difficulty on a test.
An expert at the University of California explains: "With almost all students, relaxation andless stress are felt after taking our program. Most of them experience better control during theirtests. Almost all have some improvement. With some, the improvement is very great."
To "blank out" is probably___________.

A.to be like a blanket
B.to be sure of an answer
C.to be unable to think clearly
D.to show knowledge to the teacher