问GRE阅读36套的一道题文章内容：According to astronomer S.A.Phinney,kicking a rock hard enough to free it from Earth's gravity would require a meteorite capable of making a crater more than 60 miles across.Moreover,even if Earth rocks wer

问GRE阅读36套的一道题文章内容：According to astronomer S.A.Phinney,kicking a rock hard enough to free it from Earth's gravity would require a meteorite capable of making a crater more than 60 miles across.Moreover,even if Earth rocks wer
问GRE阅读36套的一道题
文章内容：
According to astronomer S.A.Phinney,kicking a rock
hard enough to free it from Earth's gravity would require
a meteorite capable of making a crater more than 60 miles
across.Moreover,even if Earth rocks were freed by
meteorite i mpact,Mars's orbit is much larger than
Earth's,
so Phinney estimates that the probability of these rocks
hitting Mars is about one-tenth as great as that of Mars's
rocks hitting Earth.To demonstrate this estimate,Phinney
used a computer to calculate where 1,000 hypothetical
particles would go if ejected from Earth in random
directions.He found that 17 of the 1,000 particles would
hit Mars.
Which of the following,if true,would cast most
doubt on Phinney's esti mate of the
probability of
Earth rocks hitting Mars?A
A Rather than going in random directions,
about
25 percent of all particles ejected from Earth
go in the same direction into space.
为何A就削弱原文意思?A只是说不是随机发射,但不是随机发射未必就一定会撞到火星呀?

问GRE阅读36套的一道题文章内容：According to astronomer S.A.Phinney,kicking a rock hard enough to free it from Earth's gravity would require a meteorite capable of making a crater more than 60 miles across.Moreover,even if Earth rocks wer
其他几个选项是什么?

Hi, Mzdawn!

This is a logical proposition. Whether you are in court or exam, you may pay more attention to two aspects when casting doubts. 

prerequisite and deduction

prerequisite is the requisite you propose in order to deduct. In other words, if the condition consisting these necessities is not met, your deduction is fauty.

deduction is the "conditional conclusion" you achieve only if the prerequisites are all true.

Then we shall scrutinize this proposition.

To demonstrate this estimate, Phinney

used a computer to calculate where 1,000 hypothetical

particles would go if ejected from Earth in random

directions. He found that 17 of the 1,000 particles would

hit Mars.

Prerequisite: "1,000" "hypothetical" “random"

Deduction: few of them would hit Mars

So according to the analysis, we should contend those following arguments are solid.

1. If in reality, far more than "1000" particles are ejected from Earth, then, the deduction is fauty.
   

   2.  If in practice, the actual particles have different  properties compared to the "hypothetical" ones, then, the duduction is only a conjecture.

   3. If in actuality, the particles are projected not "randomly", then, the experiment does not reflect real-world condition.

Searching for the "prerequisite" and "deduction" and underscoring them during tests, I believe you can get the correct answer!

                                                                                      May you be enrolled in a good school!

                                                                                                        Sincerely, Kyon