1.WhenIpassedthenextroom,Iheardsomeone.ButbeforethatIhadneverheardanyoneA.sing;singB.singing;tosingC.singsing;singD.sing;singIoftenhearthesoundofchildren(play)intheparknearby

Question

1.When I passed the next room,I heard someone_____.But before that I had never heard anyone____
A.sing;sing B.singing;to sing C.singsing;sing D.sing;sing
I often hear the sound of children ____(play)in the park nearby

Answer 1

c听到某人正在做某事,ING形式,后一个是现在时hear sb do sth.
原型,因为是经常听到,所以是hear sb do sth.