The correct option is
C Tranquilizer
Analysing the options:
Option (A):
Artificial sweeteners are synthetic sugar substitutes. They may be derived from naturally occurring substances, such as herbs or sugar itself.
Option (B):
Tranquilizers are neurologically active drugs used to treat stress and severe or mild mental disorders.
Equanil is an example of a tranquilizer that helps in controlling depression and hypertension.
This medication is used short-term to treat symptoms of anxiety and nervousness. It acts on certain centres of the brain to help calm the nervous system.
Option (C):
Antihistamines are a class of drugs commonly used to treat symptoms of allergies, runny nose, sneezing, urticaria, etc.
Option (D):
An antifertility drug is a chemical substance that helps in suppressing the hormonal actions that promote fertility in women. These drugs reduce the chances of fertility by acting as protection.
These include birth control pills.
So, option (B) is the correct answer.