How are identical twins formed, and which option correctly describes the initial fertilization event?

Step 1: Understand the formation of identical twins. Identical twins* (monozygotic twins) develop from a single fertilized egg. This means that one sperm fertilizes one egg, forming a zygote. Early in development, this single zygote then splits into two separate embryos, each developing into a genetically identical individual. Step 2: Evaluate the given options based on this understanding. A. two sperm cells and two egg cells: This describes the formation of fraternal twins* (dizygotic twins), where two separate eggs are fertilized by two separate sperm. B. one sperm cell and two egg cells*: This scenario is not how twins are formed. C. two sperm cells and one egg cell*: This is a rare and usually non-viable event called polyspermy, not the mechanism for identical twin formation. D. one sperm cell and one egg cell*: This correctly describes the initial fertilization event that leads to a single zygote, which then divides to form identical twins. The final answer is D. one sperm cell and one egg cell That's 2 down. 3 left today — send the next one.