Not an expert, but here is the way I looked at the argument.
The college observed an “effect.” They see that 75% of the people sign up a week before the classes start.
The college concludes that it will institute a Plan to offer a new class each week to “capitalize on the high level of demand” that occurs last minute (a week before the class starts).
One of the assumptions that appears to be a common pattern in a lot of “Plan - to - Goal” type arguments is the following:
The author assumes that the Plan he or she puts into place will not somehow lead to making the problem worse. The author assumes she has perfect knowledge about the scenario and that there isn’t something he or she doesn’t understand about the scenario.
In this case, the author assumes that the reason for 75% of the people signing up a week before class is because these people are procrastinors. (“High level of last minute demand”)
The author believes that the “cause”/“reason” for 75% of the class attendees signing up so late is because there exists a high level of demand a week before classes.
The GAP in this thinking is that the author is conflating two ideas: the idea that if someone signs up late for a class ———> necessarily means that the person did not expect to take the class before that last week leading up to the class.
However, just because a person signs up for a class one week before the class starts does not necessarily mean that the person did so because of “last minute” decisions. The author is assuming that people are making these last minute decisions and that offering a class each week will capitalize on these decisions. (More people will be able to sign up last minute because classes are offered each week)
If the people signing up are NOT making last minute decisions but are instead making long term plans to take a class (at what time you sign up for a class does not necessarily have any bearing on how far in advance you plan), then offering a class each week will not be capitalizing on a “last minute demand” the author believes exists.
For this reason, B is the required assumption.
Posted from my mobile device