Only answer if your are 100% sure.

Answer:
It is zero
Step-by-step explanation:
The attatched should help you understand discriminants:
Answer:C
Step-by-step explanation:
If the discriminant is negative you will have no real roots, if it is positive it will have 2 real roots, only with a discriminant of 0 will you get only one real root. Also, for undefined discriminant that is the same as a negative answer.