Explanation
Correct answer: A.
Choice A is the best answer. The sentence emphasizes how harsh the conditions in the tundra can be, noting that the winters are especially harsh and describing the average temperatures as “frigid.”
Why the other choices are wrong
Choice B
Choice B is incorrect because the sentence explains that some animals can survive harsh tundra winters; it doesn’t emphasize how harsh the conditions can be.
Choice C
Choice C is incorrect because the sentence specifies how many different kinds of plants can live in the tundra; it doesn’t emphasize how harsh the conditions in the tundra can be.
Choice D
Choice D is incorrect because the sentence explains that both plants and animals can survive in the tundra; it doesn’t emphasize how harsh the conditions in the tundra can be.