$ADA prioritizes which of the following?

a) Sustainability and security.
b) Unlimited scalability with proof-of-work.
c) High transaction fees for miners.
d) Solely fast transactions, ignoring energy efficiency.

Correct Answer: a) Sustainability and security.

Explanation: Cardano ($ADA) uses a proof-of-stake mechanism to ensure environmentally friendly and secure blockchain operations while maintaining scalability.