An active immune system recruits many cells of the affected tissue to kill off the disease-causing microbes. What is this recruitment process known as?

When the immune system recruits cells, it actually prepares the body to fight microbes of diseases. This is called immunisation. Vaccination is the process of giving the medicine/formulation to bring immunity. Inflammation refers to swelling which may be a consequence of some infection, i.e. attack of infectious agents. Hence, only option (3) is the correct answer.