All you have to do is combine like terms/variables.
C) 7x^2 + 2x - 2 would be the correct answer.
Since 7x^2 is the only variable with an exponent, it stays the same. Now you add -2x and +4x since four is positive and larger than 2, that means the answer will be positive. That would make it 2x and -3 is the only number which remains the same.