The correct answer as to which observation of dihybrid cross led to Mendel's law of independent assortment would be the presence of one trait that did not affect the presence of another. The correct option would be D.
The law of independent assortment states that traits are inherited independently.
This means that one gene codes for one trait and genes do not influence each other. For example, a gene for eye color would be independently inherited from a gene for skin color.
Mendel arrived at this observation when he carried out a cross involving two traits. Each trait followed the same phenotypic ratio as if they were a monohybrid cross. It does not matter the number of trait involved in the cross, they never influenced each other.
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