高中英语语法2道
Mysister,aninexperiencedrider,wasfoundsittingonthebicycle____tobalanceis.
A.havingtried
B.trying
C.totry
D.tried
请问这道题为什么选A不选B
Ifthereisalotofwork______.I’mhappytojustkeeponuntilitiffinished.
A.todo
B.tobedoing
C.done
D.doing
请问这道题为什么选B不选A