Final answer:
The proper sequence for cell differentiation and specialization starts with fertilization, followed by mitosis, and then differentiation.
Step-by-step explanation:
The correct order of events for cell differentiation and specializations is: fertilization, mitosis, differentiation. Therefore, the correct choice is a) Fertilization, mitosis, differentiation. Through this sequence of events, cells go from being a single fertilized egg, or zygote, through repeated cycles of mitosis which increases cell number, and then through differentiation where cells become specialized into the various cell types required for the organism's body plan and function.