It's C. In order to be in standard form you have to have all your exponents in descending order. They don't all have to be there in order, the ones that are just have to go from highest to lowest.
Recall the Maclaurin expansion for cos(x), valid for all real x :

Then replacing x with √5 x (I'm assuming you mean √5 times x, and not √(5x)) gives

The first 3 terms of the series are

and the general n-th term is as shown in the series.
In case you did mean cos(√(5x)), we would instead end up with

which amounts to replacing the x with √x in the expansion of cos(√5 x) :

31,680 feet per hour.
There are 5280 feet in a mile, so 6(5280)=31,680
132 degrees
37 degrees
169 degrees
180 degrees