Answer: Option (D) is the correct answer.
Step-by-step explanation:
When a person thinks, feels or acts in ways which are not normal or which are unusual in many ways then this activity is considered as symptoms of a person's behavior.
For example, a women argues with everyone without any reason.
So, when a person suffers from some any mental disorder then he doesn't know what he is saying, doing or expressing.
Hence, we can conclude that ways of thinking, feeling, or acting that are unusual are symptoms of a mental disorder.