What happens to cause only one egg to form?

An identical twin pregnancy occurs when the fertilized egg splits. Sometimes, a single embryo splits after it's been fertilized. are you talking about that or something else

Explanation:

cramming before a final is bad because it makes a student's stress level higher. students who embrace cramming to get through a final exam week find themselves struggling to perform consistently, once the brain adjusts to prolonged sleep deprivation.

answer; a male inherits only one allele of the x-linked gene controlling hair color;