Answer:
Leukocytes.
Step-by-step explanation:
The infection can occur in the body by the pathogens or by an injury. The immune cells of the body against these infection and protect the individual's body.
The leukocytes are the main immune cells present in the body that plays a role in providing immunity. The number of leukocytes increases in case of the infection.
Thus, the correct answer is option (4).