Choose the correct particle back away: move backwards from sth/sb
back down: give in, accept defeat
back up: make a copy of a file/programme etc.
back sb up: give support to sb
back out: decide not to do sth
call sb back: return sb's phone call
call off: cancel
carry on: continue
carry out: do sth as planned (a plan/order/threat etc.),
perform or conduct (repairs, research, tests, etc.)
1. The guard asked the passengers to back away/
down from the edge of the train platform.
2. The school carried on/out a fire safety drill.
3. Despite his accident, he carried on/out climbing.
4. Back up out your computer files regularly.
5. The match was called off/back due to heavy rain.
6. She backed down/out of the race in the end.
