In the advanced course students must take performance tests at monthly______.
172. Since the disaster of September 11, American economy has got into a jam. The underlined part probably means _____.
171. You should put down your jacket, otherwise both of you will have a quarrel. That will make things worse. The underlined part probably means _____.
170. So long as you work hard enough, a(an) _____ rod can be ground into a needle. (prov.)
169. The people performing all play different _______ and three of them sing, too.
168. Read the ______ on the box carefully before you take the medicine.