Question

alternative means :
serving or used in place of another
set forth authoritatively as obligatory
being in captivity
easy to perceive

Explanation:

The word "alternative" means something that can be used instead of another thing. Among the given options, "serving or used in place of another" is the correct meaning. The other options: "set forth authoritatively as obligatory" is more related to words like "mandatory"; "being in captivity" is about being imprisoned; "easy to perceive" is about being obvious or clear, which are not the meanings of "alternative".

Answer:

serving or used in place of another