Function on their own unicellular organisms must do what
a do all jobs for survival
b make tissue
c perform specialized task
d work with other cells

The correct answer will be option-A.

Explanation:

The unicellular organisms are made up of only one cell which can perform all the functions of life.

In the primordial time, the unicellular cells acquired many traits to survive which included the coordination with other cells to perform a specialized task. This specialized task could be performed by the cells which perform the same functions by coordination and forming a structure called tissue. These characteristics are still present in the unicellular organisms.

To survive a unicellular cell can perform all the functions provided in the question and thus, option-A is the answer.