Answer:
The correct answer is - temporal relationship.
Explanation:
Temporal relationship is the timing between a variable or factor and an outcome or result that can be used to assign a reason for the relationship. This type of causal relationship that is temporal relationship cannot be assessed in a cross-sectional study.
As it can not be assessed in the cross-sectional study so, it is not possible to assess if happy people are more likely to get married or marriage leads to happiness.