Answer:
c.They rank-order the units of analysis in terms of specific variables
Explanation:
An index is a way of compiling one score from a variety of questions or statement that represents a belief, feeling or attitude.
Scales on the other hand measure levels of intensity at a variable level like how much a person agrees or disagrees with a particular statement.
The one thing common to both indexes and scales is that
They rank-order the units of analysis in terms of specific variables.