2. Let \( X=\{a, b, c \). Which of the following collections are topologies for \( X \) ? If a collection is not a topology, explain why it is not.
(a) \( \{X,\{a\},\{b\},\{a, b\}\} \)
(b) \( \{X, \phi,\{a\},\{b\}\} \)
(c) \( \{X, \phi,\{a\}\} \)
(d) \( \{X, \phi,\{a, b\},\{b, c\}\} \)