If $f: A \rightarrow B, g: B \rightarrow C$ are functions such that $g \circ f: A \rightarrow C$ is onto,…
If $f: A \rightarrow B, g: B \rightarrow C$ are functions such that $g \circ f: A \rightarrow C$ is onto, then a necessary condition is
f is onto
g is onto
both f, g are onto
neither f nor g is onto
Solution
If functions $f: A \rightarrow B$ and $g: B \rightarrow C$, such that gof : $A \rightarrow C$ is onto, then it is necessary that ' $g$ ' is onto. Hence, option (b) is correct.