In set-builder method the null set is represented by
(a) \(\{\}\)
(b) \(\Phi\)
(c) \(\{x:x\ne x\}\)
(d) \(\{x:x=x\}\)
Solution
A null set contains no element.
In set-builder form,
\[ \{x:x\ne x\} \]
means the set of all \(x\) such that \(x\) is not equal to itself.
This is impossible for any element.
Therefore, the set contains no element.
Answer
\[ \boxed{\{x:x\ne x\}} \]
Correct option: (c)