The correct option is C 2
Since, the given equation have more than two roots so this is identity.
Thus given equation is satisfied for all values of x, so all the coeffients must be zero. Then,
a2−a−2=0⇒a=−1,2
a2−4=0⇒a=−2,2
a2−3a+2=0⇒a=1,2
Therefore, the common value of a=2