Why did President Eisenhower take three weeks to send federal troops to ensure the Little Rock Nine could enter school?A) Governor Orville Faubus...

The best answer to this (of the options that you have
given us) is B.

When the crisis over the desegregation of
Little Rock Central High began, Pres. Eisenhower met with Gov. Orval Faubus.  Pres.
Eisenhower believed Faubus when Faubus promised that he would comply with the court
order.  As the link below says,

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Faubus gave assurances that he would not resist
further attempts at desegregation but later betrayed the
president.

Eisenhower had
trusted Faubus and had hoped that the situation could be resolved without resorting to
force, but he eventually found out that he was wrong.

One
reason why Eisenhower acted in this way was the fact that he did not think the federal
government should be telling the states what to do.  As the link below also
says,

readability="7">

Eisenhower believed that southern states should
voluntarily promote racial equality, and that federal intervention should only be used
as a last resort.

As these
quotes show, Eisenhower wanted to avoid federal involvement and so he was inclined to
believe Faubus's promises.

Therefore, the best answer is
B.