Using KNOCK UP, KNOCK OFF and KNOCK ON

[b2]

English Language Tests, Intermediate level

ESL/EFL Test #186 "Idioms with the phrasal verb knock", question 7

There wasn't much food in the cupboard, but I managed to ......... a meal for myself.

(a) knock out
(b) knock up
(c) knock off
(d) knock on

English Language Tests, Intermediate level

ESL/EFL Test #186 "Idioms with the phrasal verb knock", answer 7

There wasn't much food in the cupboard, but I managed to knock up a meal for myself.

Correct answer: (b) knock up

Your answer was: ?
_________________________

Hi,
could you please explain me when do we use knockup, knock off &knock on?
thanks

b2

[Conchita]

Here are some of the definitions of these verbs:

To knock up is to make ready

To knock off is to hit (something) so that it falls off

To knock on (e.g. the door) is to hit the door with your knuckles to call attention