only N, E, Q are countably infinite sets.. R is uncountably infinite set.. based on cardinality, sets either have finite size, countably infinite(whose cardinality is denoted by aleph null) and uncountably infinite (whose cardinality is denoted by $\epsilon$)... since first 3 are countably infinite sets, so all these 3 should have same cardinality aleph null.. set of real numbers is uncountably infinite set whose cardinality is more than aleph null..