Genetic variation happens when one organism in the population mates with a genetically different organism. Same species, different genetics such as color or height/weight.
Sex linked traits can only be held on the X chromosomes, so males only need one while females need two. Since the daughter has it, it must mean the mother is a carrier and has one normal X chromosome and another with the recessive trait (c).
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They all take nutrients out of the soil which leaves the soil infertile