Question

2道单选题The missing boy was last seen ___ near the river.A.play

Answer 1

1.see somebody do/doing 看到某人在做某事,用playing表示最后被人看到时,正在河边玩,选A

2.hear somebody do/doing听到某人做某事,

可以用singing,或是to be singing,选D

他经常被人听到在唱国际...（ing形式表示习惯性的行为）