Meaning of "cheer somebody on/up"

[Koala]

English Language Tests, Intermediate level

ESL/EFL Test #191 "Phrasal Verbs (C)", question 2

Randy always tried to ......... on rainy days.

(a) cheer everyone on
(b) cheer everyone up
(c) cheer everyone

English Language Tests, Intermediate level

ESL/EFL Test #191 "Phrasal Verbs (C)", answer 2

Randy always tried to cheer everyone up on rainy days.

Correct answer: (b) cheer everyone up
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I don't know what "cheer somebody on/up" means?

Koala

[Conchita]

To cheer up means 'to make/become happier':

cheer up!, don't be miserable;
he cheered up considerably when he had had a drink.

To cheer someone (on) is to shout encouragement:

the crowd cheered on the home team.