why use single instead of using solitary?

[johnxyy]

Synonym Search, Intermediate level

ESL/EFL Test #114 "Synonyms for solitary and single", question 9

He can afford the best apartment in the hotel but he always takes a ......... room.

(a) lonesome
(b) unaccompanied
(c) single
(d) solitary

Synonym Search, Intermediate level

ESL/EFL Test #114 "Synonyms for solitary and single", answer 9

He can afford the best apartment in the hotel but he always takes a single room.

Correct answer: (c) single

Your answer was: incorrect
He can afford the best apartment in the hotel but he always takes a solitary room.
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why use single instead of using solitary?

thx
johnxyy

[Mister Micawber]

.
That's what they are called in the hospitality industry: 'single rooms' (as opposed to 'double rooms' or 'suites').
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mr. Micawber