help me please

1. Among the following distributions, the discrete distribution is (). A. B(3,0.5) B. U(0,3) C. N(0,3) D. F2,2 2. Let X,Y be two independent random variables satisfying standard normal distributions, then the distribution satisfied by X2+Y2 is ( ) A. N(0,1) B. 22 C. Exp(1/2) D. P(2) 3. The limit of a cumulative distribution function of a random variable at + is A. 0 B. 1/2 C. 1 D. 3/2 4. If a random variable X has a mean and a variance 2, according to Chebyshev's inequality, the probability P(X2) ( ). A. 4/5 B. 5/6 C. 6/7 D. 3/4 5. Let X be the number of heads obtained in the experiment that a fair coin is tossed 5 times, then X satisfies A. Normal distribution B. Negative Binomial distribution C. Uniform distribution D. Binomial distribution 1 6