Your answer is D. untestable and open to change
The keystone species is the one at the bottom of the pyramid, if we look at it like a pyramid. If the grass dies, then the deer cannot get food and die, and the predator cannot eat and dies, and the whole ecosystem can fall apart.
Answer: Of 125 students with hitchhiker's thumbs, 1/3rd would be homozygous dominant (41 students)
HH homozygous dominant
Hh heterozygous dominant
hH heterozygous dominant
hh homozygous recessive
