Question

If $f:A\to B$ is a constant function which is onto then $B$ is

• A. a singleton set
• B. a null set
• C. an infinite set
• D. a finite set

Answer 1

Answer: (A)

a singleton set

$f\left(x\right)$ is a constant fucntion $\Rightarrow$ Range of $f\left(x\right)$ is a singleton set.
For $f$ to be an onto function, Co domain $B$ should be equal to Range.
$\therefore B$ is a singleton set.