HI can someone plss finish these sentences (it could be one sentence or two) I rlly need help with it.

1. The doctor remained placid during the surgery because . . .
2. Driving in a car is the predominant method of travel because . . .
3. It took some practice for the group to sing in unison because . . .
4. The nation was impoverished because . . .
5. Those clouds on the horizon appear ominous because . . .