why correct answer is road why not others?

[Nathan]

English Language Tests, Intermediate level

ESL/EFL Test #292 "English Slang Idioms (14)", question 2

He decided to flag down the waitress and order one for the ..........

(a) road
(b) posterity
(c) head
(d) cuff

English Language Tests, Intermediate level

ESL/EFL Test #292 "English Slang Idioms (14)", answer 2

He decided to flag down the waitress and order one for the road.

Correct answer: (a) road
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why correct answer is road why not others?

Nathan

[Linda]

Hello,
"Order one for the road" is a common expression that refers to "something given to someone when that person is leaving so that he or she may enjoy it during the trip home." These questions test the students' abilities to find the common "English Slang Idioms."
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