If a,b,c,d, and e are real numbers and a≠0, then the equation of

$\displaystyle

ax^7+bx^5+cx^3+dx+e=0$ has

A. No Real Roots

B. At least One Real Root

C. An Odd number of non-real Roots

D. Only One Real Root

E. No Positive Real Roots.

I understand the basic concept of roots, where x is a number such that f(x)=0, but how would you apply that to this problem?

Thanks.