Choose your answer from:
(1). light bulbs.
(2). waves.
(3). wind.
(4). headphones.
(5). rivers.
(6). coal.
(7). motors.
(8). viruses.

Fact 1: Tidal energy can be used to produce electricity. Fact 2: Ocean thermal is energy derived from waves and also from tidal waves. Given the two facts above, what can be used to produce electricity?
Answer:
(2).