Explanation:

- Let’s break it down: a compound with exactly two carbon–carbon double bonds is called a diene. That’s your answer.

- Option 2: Dienes

Dienes literally means “two enes,” so: two double bonds. Couldn’t be clearer.

- Option 1: Terpenes

Interesting molecules, found in plants, often with isoprene units and sometimes multiple double bonds—but not always just two, and that’s not the core definition.

- Option 3: Trialkyne

“Tri” for three, “yne” for triple bonds. So this is all about molecules with three triple bonds. Not what you’re looking for here.

- Option 4: Dialkyne

“Di” for two, “yne” for triple bonds. This refers to two triple bonds between carbons, not double bonds.

So, you nailed it: dienes have exactly two double bonds between carbon atoms. Nothing else in those options fits.