Assume that a cross is made between AaBb and aabb plants and that the offspring fall into approximately equal numbers of the following groups: AaBb, Aabb, aaBb, aabb. These results are consistent with the following circumstance:

alternation of generations
independent assortment
incomplete dominance
complete linkage

Independent assortment.

Explanation:

Law of independent assortment is one of the laws that Mendel proposed in genetics. This law states that the alleles of two or more different genes get sorted into gametes independent of each other i.e. the alleles of two different genes do not influence each other at the time of gametogenesis.

For example, in this question when parents having allelic combinations AaBb and aabb are crossed they produced offsprings with allelic combinations AaBb, Aabb, aaBb and aabb. It simply indicates that the alleles of traits controlled by alleles Aa & Bb are sorting into any of the 4 gametes which are being produced. If they were not assorting independently then gametes with Aabb and aaBb combinations which are different than parents would not have produced.

d. groundwater flows through the subsoil and deposits minerals.