Elbows and knees would be the answer
<span>Having standard written research protocols is the correct answer. ;)</span>
Basically, there is a presentation of types of food and the amount of those foods over 50 years in this graph. This means the graph is showing amounts of certain foods over the time period. I'm guessing that basing off of the the previous text you're just noting a change in the breaks of birds based off of the diet available to them at certain times. The adaptations and natural selection will explain the changes because due to certain limited and available foods the diet of the birds change.
The children were given the recessive traits from their mother and the dominant traits from their father because the genes mix when they have children.
