Put the herbs in brackets into the correct tense:
a. When the boss (to enter) the office, my colleagues (to discuss) in a whisper.
b. Grandpa (to buy) a lamb last week.
c. (It to snow) since last night?
d. I (already, to paint) the walls of the house.
e. The girl (not, to dance) while her sisters (to sing).
f. The hunters (to leave) the forest before it (to get) dark.