What is one of the weaknesses of the Bubble model

Amale bird-of-paradise uses a dance to attract mates in which it flaps its tail feathers on the ground and jumps around a potential female mate. a different male bird-of-paradise does a similar dance but it jumps around the female in the opposite direction. the female bird is only attracted to one style of dance, in one direction. this is an example of speciation.

Acceleration is a direct result of a.) balanced forces b.) unbalanced forces c.) gravity d.) velocity

Which of these is not a nucleotide base found in dna?