The mother tears at the sight of her long lost son who was sent back by two policemen .

问题补充：

The mother tears at the sight of her long lost son, who was sent back by two policemen .

A. burst into

B. burst out

C. burst away

D. burst up

答案：

A. burst into

(答案→)B. burst out

C. burst away

D. burst up

解析：试题分析：句意为：当观众朋友们听到这个滑稽的故事时，他们突然发出了阵阵笑声

A.闯出来；突发；摆脱 B闯入；情绪的突然发作 C爆发，发生 D闯入

固定短语：burst into laughter突然笑出来

故B正确