Magical Cook, this is my approach to solve the SC -
one quarter that - one quarter of 4000. So it becomes more than 1. Right? And it is also countable. So B and C can be the best option to chose. But in B, it is having 'AS' with it and it does not have any sense. So C will be the best option to chose.

By the way, Magical Cook request you to provide the OA in Spolier - the button coming below on the right hand side of Subject text box.

But I wonder what the amount refer to in C ? drive-in should be countable...

Nop, Magical Cook! Probably u r not getting what I want to mean otherwise I am not getting u by ur stmt -

ut I wonder what the amount refer to in C ? drive-in should be countable...

Now look "drive ins" are countable and this problem deals with the property of using LESS and FEWER. We generally use FEW when the noun is countable and LESS for uncountable things! As "drive ins" is countable, so we will use "FEW" for that. So the options left - B and C. Now in B, grammatically wrong use of AS. So cut out this option and the only option left is - C. So C is the best option to chose.
This comes according to my understanding!

Hi Magical Cook
Could u please provide the source for this Q. As far as i know i think amount is not countable. So would like to know the source.

Thanks
Preeti