Concept:
The caste system is based on hereditary social status assigned at birth.
Step 1:
Ascription means a social status assigned to a person by birth rather than achieved through effort.
Step 2:
In the caste system, membership is determined by birth and cannot easily be changed.
Step 3:
Because caste status is inherited, sociologists describe caste as an ascriptive system.
Step 4:
• Industry relates to economic activity.
• Gerontocracy means rule by elders.
• Gender is a social category but not the defining feature of caste.
Step 5:
Therefore, the correct answer is Ascription.
\[
\boxed{\text{(1) Ascription}}
\]