A proposed change to federal income tax laws would eliminate deduction

A proposed change to federal income tax laws would eliminate deductions from
taxable income for donations a taxpayer has made to charitable and
educational institutions. If this change were adopted, wealthy individuals
would no longer be permitted such deductions. Therefore, many charitable
and educational institutions would have to reduce services, and some would
have to close their doors.

The argument above assumes which of the following?

(A) Without the incentives offered by federal income tax laws, at least some
wealthy individuals would not donate as much money to charitable and
educational institutions as they otherwise would have.
(B) Money contributed by individuals who make their donations because of
provisions in the federal tax laws provides the only source of funding for
many charitable and educational institutions. - In such case many would have closed doors. But my argument does'nt say that.
(C) The primary reason for not adopting the proposed change in the federal
income tax laws cited above is to protect wealthy individuals from having to
pay higher taxes.
(D) Wealthy individuals who donate money to charitable and educational
institutions are the only individuals who donate money to such institutions.
(E) Income tax laws should be changed to make donations to charitable and
educational institutions the only permissible deductions from taxable
income.

OA is A.
This is an OG 10 question.
OE:

The passage argues that charitable and educational institutions, part of whose income comes from donations,
would be negatively affected if wealthy individuals could not count such donations as deductions from their
income. The question asks you to identify an assumption of the argument-that is, something that has to be true
in order for the evidence presented to establish the conclusion.
Choice A is the best answer, since if this statement is false, all wealthy individuals would, even without the
incentive provided by federal tax laws, donate as much money as they do now. In that case, the evidence used
in the argument provides no support for the conclusion.
Choice B is not assumed: the argument need only assume that many institutions depend heavily, but not
necessarily exclusively, on donations from such individuals. Choice C is incorrect given that the argument is
concerned only with the consequences of the proposed change and makes no assumption about any reasons
for making or not making the change. Choice D is not assumed: as far as the argument is concerned, there can
be many other individuals who donate money to the institutions. Choice E is incorrect since the argument, being
about the consequences of the particular proposed change, does not make any assumption about what
alternative changes to the tax laws ought to be made.