#### Answer

Ca

#### Work Step by Step

Mass number A= Number of protons+ Number of neutrons.
Let the number of protons be $x$.
Then,
$A=44=(x+4)+(x)= 2x+4$
$\implies x=\frac{44-4}{2}=20$
Number of protons= 20= Atomic number Z.
The element with $Z=20$ is Calcium (Ca).