问题补充：
Seeing the stranger , the frightened baby couldn’t help crying.
A. burst in; bursting into
B. burst into; burst out
C. break in; bursting out
D. burst into; burst out
答案：
A. burst in; bursting into
B. burst into; burst out
C. break in; bursting out
D. burst into; burst out
解析：burst into意思是：爆发成；突然……起来。号啕大哭是burst into tears。特别介绍几个相同意思的词组，burst out，break into均可表示“突然……起来”的意思，区别在于burst into及break into后必须接名词，而burst out后须接动名词或接into再接名词。break in 更强调破门而入。句意：这个受惊的孩子看到陌生人破门而入，情不自禁的大哭起来。
