Solve the Problem $P _ { n }$ For an Appropriate Value Of

Multiple Choice

Solve the problem.
-Determine which of the following sets is a subspace of $P _ { n }$ for an appropriate value of $n$ .
A: All polynomials of the form $p ( t ) = a + b t ^ { 2 }$ , where $a$ and $b$ are in $R$
B: All polynomials of degree exactly 4 , with real coefficients
C: All polynomials of degree at most 4 , with positive coefficients

A) C only
B) $A$ and B
C) A only
D) B only