Which of the following are examples of null set?

{ y : y is a point common to any two parallel lines}

Answer

Let E (y : y is a point common to any two parallel lines)
Two parallel lines do not meet and as such have no common point.
$rightwards double arrow$ $space space space space space straight E space space equals space open curly brackets space space close curly brackets space space equals space straight ϕ$
Hence, E is a null set.