The correct option is A a=b=c=0
Any equation is called an identity iff the equation holds true for all values of the variable.
∴ For any polynomial equation anxn+an−1xn−1+⋯+a1x1+a0=0 iff all the coefficients of the polynomial equation is equal to 0
⇒an=an−1=an−2=⋯=a1=a0
Thus, for our equation to be identity:
a=b=c=0