(i) The infinite concentric circles can be drawn in a plane. Thus it is an infinite set.
(ii) Since, there are just 26 letters in English Alphabets. Thus it is finite set.
(iii) Since, it is an infinite set because, natural numbers greater than 5 is infinite.
(iv) It is a finite set. Here, natural numbers start from 1 and there are 199 numbers less than 200. Thus it is a finite set.
(v) It is an infinite set. Because integers less than 5 are infinite therefore it is an infinite set.
(vi) Since, it is an infinite set. Because between two real numbers, there are infinite real numbers.