A biodegradable substance is one that can be broken down by microorganisms.
Microorganisms such as bacteria and fungi decompose biodegradable materials into simpler substances.
A biodegradable detergent is therefore a detergent that does not persist in the environment for a long time.
It is easily decomposed by microorganisms.
Branched chain alkyl benzene detergents are generally less biodegradable.
Straight chain alkyl benzene detergents are more biodegradable, but the definition of biodegradable detergent is that it is decomposed by microorganisms.
Therefore, the correct answer is:
\[
\text{Is easily decomposed by microorganisms}.
\]