meaning of 'a loose cannon'

[dangg]

English Language Tests, Intermediate level

ESL/EFL Test #290 "English Slang Idioms (12)", question 5

"I don't think I'll go out drinking with James again. He is too much of a ......... cannon when he gets drunk," Leah said to Josie.

(a) rusty
(b) loose
(c) tight
(d) big

English Language Tests, Intermediate level

ESL/EFL Test #290 "English Slang Idioms (12)", answer 5

"I don't think I'll go out drinking with James again. He is too much of a loose cannon when he gets drunk," Leah said to Josie.

Correct answer: (b) loose
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can you explain to me the question?

dang

[Beeesneees]

'a loose cannon' is a term used to describe someone who acts erratically (in an unexpected or unpredictable way).

When Ben gets drunk, he is unpredictable so Leah doesn't want to go out with him.
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Cheers m' dears!