Question

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related physics
the idea of two animals combining to form a new species, called a hybrid, dates as far back as greek mythology. the chimera, for example, is a fire - breathing monster that has the head of a lion, the tail of a snake, and the head of a goat. while that may sound like the stuff of fiction, hybrid forms of living organisms have existed throughout evolutionary history. scientists estimate that about ten percent of all animals may once in a while breed with other animals.
sometimes, animal hybrids occur naturally. for example, climate changes force new species to migrate to new habitats. when that happens, animals of different species may mate by accident. sometimes, there are not enough mates for an animal, so it may seek out a member of a different species. one such naturally occurring hybrid is the pizzly—the product of a female polar bear mating with a male grizzly bear.
not all hybrids occur naturally, however. when humans hold animals in captivity, they have experimented with crossbreeding. one familiar animal hybrid is the common mule, which is the cross between a female horse and a male donkey. conversely, a female donkey and a male horse make a hybrid animal called a hinny. an example of a successful hybrid is the beefalo—a cross between a female buffalo and a bull (a male cow). this hybrid animal has the temperament of a cow but the more efficient digestive system of a buffalo, which results in a low - fat meat.
question 4
what phrase could best replace the phrase once in a while in paragraph 1?
select one:
o a. occasionally
o b. never
o c. rarely
o d. frequently
question 5
according to this selection, which animals make up a chimera?
select one:
o a. a female horse and a male donkey
o b. a lion, snake, and goat
o c. a polar bear and a grizzly bear
o d. a female buffalo and a bull
question 6
according to the text, why does climate change result in new hybrid animals?
select one:
o a. it forces animals to mate with different species.
o b. it causes animals to die at a young age.
o c. it makes humans experiment with crossbreeding.
o d. it helps animals to eat better and become stronger.

Explanation:

• For Question 4: "once in a while" means from time to time, which is similar to "occasionally".
• For Question 5: The text clearly states that a chimera has the head of a lion, the tail of a snake, and the head of a goat.
• For Question 6: The text mentions that climate - change forces new species to migrate to new habitats, and animals of different species may mate by accident, so it forces animals to mate with different species.

Answer:

Question 4: a. occasionally
Question 5: b. a lion, snake, and goat
Question 6: a. It forces animals to mate with different species.