A. is
B. was
C. were
D. be
A. sing
B. sings
C. are singing
D. sang
A. gives
B. gave
C. give
D. giving
A. have
B. has
C. had
D. was
A. is
B. was
C. were
D. be
A. has
B. have
C. had
D. was
A. wait
B. waits
C. waiting
D. were waiting
A. learn
B. learned
C. have learned
D. learning
A. has
B. have
C. had
D. was
A. have
B. had
C. has
D. having