语法与词汇 4.The market for dust masks and air purifiers is______in Beijing because the capital has been shrouded for several days in thick fog and haze.

【正确答案】 A

【答案解析】四个选项的意思分别是：boom迅速发展，兴旺；loom隐约地出现，阴森地逼近；doom命中注定，宣告；zoom突然扩大，急速上升。句意是，北京防尘面罩和空气净化器市场正在迅速发展，因为首都数天来直笼罩在雾霾中。根据句意推出正确答案是A选项。