Which of the following integrals give the area of the unit circle a. integral^1_-1integral^squareroot 1-x^2_-squareroot 1-x^2 dy dx b. integral^1_-1integral^squareroot 1-x^2_-squareroot 1-x^2 s dy dx c. integral^2pi_0integral^1_0 r dr d theta integral 2pi_0integral^1_0dr d theta d. integral^1_0integral^2pi_0 r d theta dr e. integral^1_0integral^2pi_0 d theta dr