The random variable x has a probability distribution p(x) of the form P(x=r)=⎩⎨⎧rk,(r−1)k,0,if r≤2,if 2<r≤4,otherwise, where r∈N∪{0} and k∈R, where N is the set of natural numbers. Then:
(A) k=91
(B) P(2≤x≤3)=21
(C) P(x=4)=31
(D) P(x>1)=87
Choose the correct answer from the options given below.