Choose the correct one.

• Knock something off (something)

Meaning:
1. to take a particular amount away from a price.
Example: The manager knocked $5 off because it was damaged.

2. to stop working, usually at the end of the day.
Example: What time do you knock off work?

3. to steal something
Example: He was caught selling knocked-off car radios in the pub.

4. knock someone off: 
: to murder someone
Example: He hired a hitman to knock off a business rival.

Source: Cambridge Dictionary.