Which is considered a scientific observation?

Question

Akon explained that cells need energy which is why animals eat food.
Jacinta correlated that high sweat levels were due to a high heart rate.
Mahir noticed the plants he watered grew taller than those with less water.
Kai decided plants are green because of the chlorophyll used to make food.

Answer 1

Mahir noticed the plants he watered grew taller than those with less water.