SAT question Quadratic equation

[lily]

Which of the following is equal to the number of roots having the quadratic equation ?

(A)
(B)
(C)
(D)
(E)

Thanks!

[miranda]

Which of the following is equal to the number of roots having the quadratic equation ?

(A)
(B)
(C)
(D)
(E)

Thanks!

This is an easy SAT question using GDC and find the roots of the given quadratic equation.
Another way is to recognize the identity and thus the equation has one double (repeated) root.
One more way to find the correct answer is to calculate the discriminant , therefore the equation has only one double root.
Therefore the correct answer is (B).