A) Large beak size occurred as a result of mutation in each member of the population
B) The ancestors of this bird species encountered a tree with larger than the average sized seeds. They needed to develop larger beaks in order to eat the larger seeds and over time, they adapted to meet this need
C) Some members of the ancestral population had larger beaks than others. If larger beak size was advantageous, they would be more likely to survive and reproduce. As such, large beaked birds increased in frequency relative to small beaked birds
D) There is no way to explain such phenomenon in evolutionary terms
Explanation
Some members of birds had large beak. As there was natural selection, the large beaked bird increased their frequency due to their advantages over other. That’s why their number is more than the other small beaked bird