Answer:
The correct option here is A).
Step-by-step explanation:
Option A - is correct because according to the conclusion given in the argument, charitable institutions would have to reduce their services and some might have to close their doors , which means the assumption we are going to take will have a direct affect on these institutions , now if we assume that this assumption is false, that means whether this change comes or not charitable institutions will receive donations but that is not the case , so this option has to be correct.
Option B - this option is not right because it is nowhere said that these wealthy individuals are the only source of donations for charitable institution.
Option C - this option is also not correct because here no assumption is being made, the given statement is a consequence of not bringing the change.
Option D - this option is also not correct because there can be other individuals who can make donations.
Option E - this option is also not correct because here an alternative change to tax law is being talked about not the assumption of the argument.