Answer:
d) a double standard
Step-by-step explanation:
When Jeanette's parents find out her twin brother, Rex, has been sexually active, they tell him to use protection. When they find out Jeanette has been sexually active, they ground her for a month. This is an example of a double standard.
A double standard is the baised application of a rule to different class of people. For example, Jeanette's parent were strict with her regarding sexual abstinence but in the case of her brother Rex, the rule was relaxed. Her parents are having standard regarding the two of them.