The process by which cells are drawn or attracted to an area by a microbe invader is known as

chemotaxis

Explanation:

Chemotaxis is movement of the organism in the response to the chemical stimulus.

Bacteria, somatic cells and single-cell as well as multicellular organisms direct  movements of their body according to some chemicals in the environment. This is very important for the bacteria to find the food by swimming toward highest concentration of the food molecules or also to flee from the poisons.

Thus, it is a process by which various cells are drawn to the target area by a microbe invader.

nucleus

would be most reasonable answer tbh

d. organisms have cells with different shapes and functions.