Knowing she should be excited about her friend's engagement, jessica shows exaggerated excitement when she is told about it. this modification of jessica's expression is likely due to:
1. display rules.
2. the service-task function.
3. an interpersonal gap.
4. microexpression

(1) Display rules

Explanation:

 The display rules is the form of social or the culture norms which express the emotions in informal way to the others. It is the form of interaction and also the socialization standard with the other people.

 It is the process of showing reaction in the form of non verbal communication such as gesture and facial expression.

According to the given scenario, the Jessica's expression are due to the display rules as she showing exaggerated excitement while told about the engagement.  

 Therefore, Option (1) is correct.

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