The transconductance of a JFET is computed at constant $$V_{DS}$$ by:

A

Ratio of change in $$I_d$$ to change of $$V_{gs}$$

B

Ratio of change in $$V_{gs}$$ to change of $$I_{d}$$

C

Product of change in $$V_{gs}$$ to change of $$I_{d}$$

D

Ratio of change in $$V_{ds}$$ to change of $$I_d$$