the old lady used to_under a big tree,waiting for her _ son to come backA:sit;missingB;sitting:missedC;sit:missedD;sitting:missing

the old lady used to_under a big tree,waiting for her _ son to come backA:sit;missingB;sitting:missedC;sit:missedD;sitting:missing
the old lady used to_under a big tree,waiting for her _ son to come back
A:sit;missing
B;sitting:missed
C;sit:missed
D;sitting:missing

the old lady used to_under a big tree,waiting for her _ son to come backA:sit;missingB;sitting:missedC;sit:missedD;sitting:missing
A
used to do 过去常常
be used to doing 习惯做……
be used to do 被用来做
a missing boy 一个失踪的男孩

lie dead

A
used to do 过去常常
missing 失踪的 missed 感到思念的