Q: What is the reason beak variation came about in birds?
Options:
- (A) By wind and rain
- (B) Attracting mates
- (C) It helps them survive
- (D) the Earth being tilted
- (E) Competing species evolving
- (F) it keeps an organism warm
- (G) To assist in flying
- (H) Warding off predators
A: So, my chain of thought: Specialization occurs when competing species evolve different adaptations. Beaks show a lot of variation and specialization for different functions. Beak variation came about because of competing species evolving different adaptations. The answer is (E).

Q: What can live in salt water?
Options:
- (A) otters
- (B) spider
- (C) amoeba
- (D) clam
- (E) alligator
- (F) ducks
- (G) goldfish
- (H) voles
A: So, my chain of thought: Mollusks live in most terrestrial, freshwater, and marine habitats. Mollusks tend to be shore-dwelling creatures. Clams tend to be shore-dwelling creatures and can live in both sea and freshwater. The answer is (D).

Q: Mammals can also generate little bursts of heat through what?
Options:
- (A) Movement of an air mass
- (B) crackling
- (C) Veins and arteries.
- (D) electromagnetic energy
- (E) house
- (F) fire
- (G) muscle contractions
- (H) aerobic capacity
A:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
So, my chain of thought: Mammals can also generate little bursts of heat by shivering. Shivering causes muscle contractions to warm the body. Mammals can also generate little bursts of heat through muscle contractions. The answer is (G).