Step 1: Put the plants in order of commissioning.
Tarapur (1969) came first, followed later by Rawatbhata, then Kalpakkam, Narora and Kaiga in the following decades.
Step 2: Pick the earliest.
Since Tarapur is earliest on this timeline, it is the correct answer to 'first' nuclear power station.
Final Answer:
The answer is (c) Tarapur.$\boxed{\text{Tarapur}}$