Even number between 21 to 98 = 22, 24, 26, 28, 30,........98.

This is a series of consecutive even numbers

According to the formula,

The average of consecutive numbers=$\frac{\mathrm{First} \mathrm{number}+\mathrm{Last} \mathrm{number}}{2}$

$$\begin{gathered} =\frac{22+98}{2} \\ =\frac{120}{2} \\ =60 \end{gathered}$$

Hence, Option D is correct.