If U={x:x∈N}, A={x:x=2n,n∈N} and B={x:x is a prime number}, then A∩B is a set with cardinality ________.
one
U={x:x∈N}
⇒U={1,2,3,4,5,...}
A={x:x=2n,n∈N}
⇒A={2,4,6,8,...}
B={x:x is a prime number}
⇒B={2,3,5,7,11,...}
⇒A∩B={2} as 2 is the only even prime number.
Hence, A∩B is a set with cardinality one.