A. comb
B. combs
C. combed
D. combing

A. learn
B. learns
C. learned
D. learning

A. buys
B. bought
C. buy
D. buying

A. did
B. does
C. do
D. had

A. is
B. are
C. was
D. be

A. leaves
B. left
C. had left
D. has left

A. go
B. goes
C. went
D. gone

A. has
B. have
C. had
D. having

A. watch
B. watches
C. watched
D. watching

A. is
B. was
C. has
D. were