A equation of conic is $ax^2+2hxy+by^2+2gx+2fy+c=0$ , where $a, b, c, f, g$ and $h$ are constants. Then which of the following statement are true?

(A) The given conic is circle if a = 0 and b = 0. 

(B) The given conic is circle if $a=b\ne0$ and h = 0.

(C) The given conic is circle if $a=b=\ne0$ and $h\ne0$ .

(D) The given conic represents a pair of real and distinct straight lines if f = g = c = 0 and $h^2-ab>0$. 

Choose the correct answer from the options given below: