Expression "as best as you can"

[Omarik]

English Language Tests, Intermediate level

ESL/EFL Test #153 "Comparison with as .... as", question 10

A wise man once said that a change is almost ......... a holiday.

(a) as good as
(b) as long as
(c) as soon as
(d) as much as

English Language Tests, Intermediate level

ESL/EFL Test #153 "Comparison with as .... as", answer 10

A wise man once said that a change is almost as good as a holiday.

Correct answer: (a) as good as
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Can I use the expression as best as you can?

Omarik

[Mister Micawber]

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I have heard it, but I think it is too casual for writing; use 'as best you can'.
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Native English teacher at Mister Micawber's