Fill in the gaps with the Past Continuous of the verbs

Fill in the gaps with the Past Continuous of the verbs in brackets.

a) The teacher __________ (not talk) when Mary arrived.
b) The pupils __________(play) when the bell rang.
c) Lucy __________ (do) her homework when someone knocked the door.
d) Marks parents __________(write) him a letter when they heard a crash.
e) Ann __________ (not sleep) when the alarm clock rang.
f) They __________(not watch) TV when their parents arrived.