True/false. indicate whether the statement is true or false. (no explanation required)
(a) let x be a positive real number. if 3 \leq √ < 3 + \varepsilon for all \varepsilon > 0, then x = 9.
(b) let s be a nonempty subset of the real numbers. if x is a boundary point of s, then x is an upper bound or a lower bound of the set s.
(c) the set of all rational numbers between √3 and √7 is a countable set.
(d) given any subset s of the real numbers, if its interior, int s, is nonempty, then s is an uncountable set.