The action of JFET in its equivalent circuit can best be represented as a

Option A: Current controlled Current source
A current-controlled current source (CCCS) means the output current is proportional to the input current. However, the operation of a JFET does not involve control of current by another current. Therefore, this option is incorrect.

Option B: Current controlled Voltage source
A current-controlled voltage source (CCVS) implies the output voltage is controlled by the input current. Since the JFET is voltage-controlled, its output voltage is not directly dependent on the current. Hence, this option is incorrect.

Option C: Voltage controlled Voltage source
A voltage-controlled voltage source (VCVS) suggests that the output voltage is influenced by the input voltage. Although the JFET is voltage-controlled, its output behavior is better described as controlling current, not voltage. Thus, this option is also incorrect.

Option D: Voltage controlled Current source
A voltage-controlled current source (VCCS) means the output current is controlled by the input voltage. In a JFET, the gate-to-source voltage controls the current flowing through the drain-source channel. This aligns with the operation of the JFET, making this option correct.

Conclusion:
The action of a JFET in its equivalent circuit can best be represented as a Voltage controlled Current source (Option D).