(a)x^2 is d correct answer becoz it is a quadratic polynomial in variable'x'. (b) is not the correct answer becoz it is not a polynomial becoz it's variable has not an integral power.. it is a rational no. and u know in polynomial he power of variable is always a positive integer. (c)is not the correct answer becoz the power of variable seems negative integer (d)is also an incorrect answer becoz there are two variables x & y.. so (a) is the correct answer. .