a. the bus had picked up ten people before the accident had occurred

b. the bus had picked up ten people before the accident was to occur

c. the bus picked up ten people before the accident had occurred

d. the bus had picked up ten people before the accident occurred

a. when did you live there

b. when you have been living there

c. how long have you been living there

d. how many years did you live there

a. would collect

b. will have collected

c. would be collected

d. will have been collecting

a. finishes

b. is finishing

c. has not finished

d. has been finishing

a. surf, goes off

b. am surfing, goes off

c. was surfing, went off

d. was surfing, was going off

a. will begin

b. is beginning

c. has begun

d. had begun

a. have been increasing

b. increase

c. were increasing

d. will be increasing

a. died

b. dead

c. been died

d. been dead

a. smoked

b. have smoked

c. has smoked

d. are smoking

a. were breaking / had stolen

b. broke / stole

c. have broken / have stolen

d. had broken / would steal