Since the molecule is able to immediately absorb the red color of the bromine, the molecule would be cycloheptene.
What is unsaturation?
Unsaturation in organic compounds refers to the presence of double or triple bonds in the compounds.
One way to test for unsaturation is to use bromine water. A saturated compound will not be able to absorb bromine because it is already saturated.
An unsaturated compound, on the other hand, will be able to absorb bromine due to the unsaturation. Therefore, the red color of bromine will disappear due to absorption.
Cycloheptane is saturated while cycloheptene is unsaturated. Thus, the latter will absorb the red color of bromine.
More on unsaturation can be found here: https://brainly.com/question/561845