A heterozygous plant with genotype Aa self-pollinates, and then its offspring also self-pollinate. Find the probability that the offspring of the offspring are tall for the following genetics systems.
1. Only plants that have two A alleles are tall.
2. Plants that has either one or two A alleles are tall.
3. Heterozygous plants are tall, and homozygous plants are short.
4. Half of heterozygous plants and one fourth of homozygous plants are tall (it depends on their position in the greenhouse).