Why cannot we use until?

[Sara]

English Language Tests, Intermediate level

ESL/EFL Test #142 "Time clauses: future tense examples", question 3

She's going to look after the cat ......... I'm away on holiday.

(a) until
(b) while
(c) before
(d) before

English Language Tests, Intermediate level

ESL/EFL Test #142 "Time clauses: future tense examples", answer 3

She's going to look after the cat while I'm away on holiday.

Correct answer: (b) while
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Why cannot we use until

Sara from iran

[Yankee]

Hi Sara

"While I'm away on holiday" talks about all of the time between the beginning and the end of the holiday.

"Until I'm away on holiday" would mean the time before the holiday begins. I am at home then, so I don't don't need anyone to look after the cat. I can do it myself.