To determine if each statement is true or false, we need to understand the concepts of subset and element membership in sets.
(a) A set is always a subset of itself.
(b) Check if the set {2,4} is an element of the set of natural numbers.
(c) Check if the set {p, q, r, s, t, u} is a subset of {p, s, u}.
(d) The empty set is a subset of any set.
A set is always a subset of itself. Therefore, \(\{f, g, k\} \subset \{f, g, k\}\) is true.
The set \(\{2, 4\}\) is not an element of the set of natural numbers \(\{1, 2, 3, 4, \ldots\}\). Therefore, \(\{2, 4\} \in \{1, 2, 3, 4, \ldots\}\) is false.
The set \(\{p, q, r, s, t, u\}\) is not a subset of \(\{p, s, u\}\) because it contains elements (q, r, t) that are not in \(\{p, s, u\}\). Therefore, \(\{p, q, r, s, t, u\} \subseteq \{p, s, u\}\) is false.
The empty set \(\varnothing\) is a subset of any set. Therefore, \(\varnothing \subseteq \{14, 18\}\) is true.
\(\boxed{\text{True, False, False, True}}\)