The Argument suggest that the school should do B Instead of A
So the assumption would be something that would suggest why B is better than A. In the sense connecting those two rogue pieces of information. We are looking for a supporter.

IMO: C
I will try to explain:
A)Parents will simplify their daily schedules in order to arrive at pickup time punctually.
Let us apply the Negation test to this :
Parents MIGHT NOT simplify their daily schedules in order to arrive at pickup time punctually.
(by rules of negation will becomes might not)
Now is this negated choice attacking the argument? I think not according to the Negated choice they might not change their schedules to come pick up or they might do it.
C)Parents will find the late pickup fee more objectionable than a tuition hike that would be necessary to pay for additional staff.
This is exactly the supporter im looking for, nevertheless lets apply the negation test to confirm our answer:
Parents MIGHT NOT find the late pickup fee more objectionable than a tuition hike that would be necessary to pay for additional staff.
This negated choice tells us that parents might not find the late pickup fee more of a problem than the resultant increase in tution fee when new staff is hired. If this were the case then the parent would be more than happy to let the school hire new staff and keep their kids for longer in school.

Im guessing you applied the negation test wrong by changing the WILL to WILL NOT, I used to make this mistake myself ...remember you have to logically negate the assumption, you should not make it the polar opposite.
Egs. For "Sweet" the polar opposite is "Sour", which includes just one type of taste "sour" . The actual logical negation of "sweet" is "not sweet", which would then include several flavors like spicy,sour,bland etc.
But note the logical negation of "not sweet" would then be "sweet" which would reduce the range of flavors from many to one.
I try to remember it by "MANY TO ONE, ONE TO MANY" - from many flavors to one flavor, from one flavor to many flavors.
Same goes for the word "ALL" though its literal meaning suggests all applies to a range in truth :
All=100(single entity) logical opposite None=0to99 (Range)
Some= 1to100(Range) None=0 (single entity)
One=1 (single) Not One= (range-everything apart from 1)
WILL=1 WILL NOT=0 (WRONG)
WILL=1 MIGHT NOT= 0 or 1(CORRECT)

It is helpful to use quantities to represent


I hope i made sense....lol!!

IMO C. Because if the fee because of picking up late is higher than the fee the parent pay for the tuition, they will choose tuition, which benefit more than fee for picking up late. Weaken the argument => assumption

Not able to follow this one.

I thought, it should be C.

Why not C?

Thanks.

The staff of Soundview school is spending more and more of its time taking care of children whose parents do not arrive to pick them up from class on time. As a result, more teachers will have to be hired. The school could, instead, charge parents a nominal fee whenever they fail to arrive to pick their children up on time. This charge would encourage punctual pickup.

Argument:
increasing tution fee did not encourage parents to pick up on time but
charging a late fee would encourage parents to pick up on time;
why is that? The answer should take both facts into consideration; The answer would be along the lines--> parents see paying late fee negatively but don't see increase in tution fee;

The closest answer is (C) ;

Coming to (A): Is not doesn't fit the bill because

1. It doesn't deal with both facts;
2. Even ignoring first fact; Just consider
charging late fee ----> encourages children to be picked up on time;
It is not neccessary that the parents come and pickup by adjusting there schedule, they just could make some other arrangement. It also not known why parents are picking up i time, may not be because of time but may be just not punctual;