Phone them vs. phone now

[Ilogical]

English Grammar Tests, Elementary Level

ESL/EFL Test #109 "Postcard: Winner", question 5

The number is 7863452 but you must phone ..........

(a) then
(b) now
(c) there

English Grammar Tests, Elementary Level

ESL/EFL Test #109 "Postcard: Winner", answer 5

The number is 7863452 but you must phone now.

Correct answer: (b) now

Your answer was: incorrect
The number is 7863452 but you must phone there.
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When the number is given, he has no need to phone at once I think ,so I think the right answer is C

[Mister Micawber]

.
You must not try to anticipate all contextual possibilities. Simply find the natural English. We do not use 'phone there' in normal conversation (we use 'phone them' or simply 'phone'), and 'but' makes the clause illogical besides.
.
_________________
Canadian-American native speaker
who teaches English for a living at Mister Micawber's
ESL cafe: Interview with Mister Micawber