1.不定冠词用在固定词组中

all of a sudden突然　a matter of course理所当然的事　as a(general)rule通常　as a matter of fact实际上　at a loss困惑　at a discount打折扣，没销路　at a time when一度　to be in a hurry匆忙　to be in a temper发脾气　to be in a position to能够　to do/make a good job of干得不错　for a loss处于苦恼中　to have a chance(an opportunity)有机会　to have a good time玩得高兴　to have a hand in参与，插手　to have a pain疼　to have a say有发言权　to have a try试一试　in a walk轻而易举地　to keep an eye on照看，密切注视　to lend a hand帮助　on a large scale大规模地　to take a walk步行　to take an interest in对……感兴趣　with a firm hand坚决地　with a view to考虑到