The poor old man with his two daughters in the street.
A. was seen to beg
B. were seen to beg
C. was seen begged
D. were seen begging
网友回答
(答案→)A. was seen to beg
B. were seen to beg
C. was seen begged
D. were seen begging
解析：句子主语是poor old man，所以谓语动词用单数，see动词用于被动语态中，宾补的不定式要还原to出来。