Following is the small signal high frequency equivalent circuit of a common source amplifier $$\frac{V_{o}}{V_{i}}$$ will be of the form
$$(K, Z_{1},a_{o},a_{1},a_{2},a_{3}$$, are constants containing circuit elements)

A

$$\frac{K(s-Z_{1})}{a_{o}+a_{1}s+a_{2} s^{2}}$$

B

$$\frac{K.s}{(a_{o}+a_{1}s+a_{2} s^{2}+a_{3} s^{2})}$$

C

$$\frac{K(s-Z_{1})}{a_{o}+a_{1}s}$$

D

$$\frac{K}{a_{o}+a_{1}s}$$