Meaning of 'Throw in one's lot with'

[Bubbas]

English Language Tests, Intermediate level

ESL/EFL Test #620 "English Slang Idioms (362)", question 9

"It seems like kids just don't turn out right in our neighborhood. James' son got good grades when he was in school, but now he's thrown his ......... in with a biker gang," Walter told Harris.

(a) blanket
(b) lot
(c) pallet
(d) towel

English Language Tests, Intermediate level

ESL/EFL Test #620 "English Slang Idioms (362)", answer 9

"It seems like kids just don't turn out right in our neighborhood. James' son got good grades when he was in school, but now he's thrown his lot in with a biker gang," Walter told Harris.

Correct answer: (b) lot

Your answer was: incorrect
"It seems like kids just don't turn out right in our neighborhood. James' son got good grades when he was in school, but now he's thrown his blanket in with a biker gang," Walter told Harris.
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What it means....thrown his lot...?

Bubba

[Mister Micawber]

'Throw in one's lot with' = join and share one's fortunes with
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Native English teacher at Mister Micawber's