goalsnr
Responding to the public’s fascination with―and sometimes undue alarm over―possible threats from asteroids,
a scale developed by astronomers rates the likelihood that a particular asteroid or comet may collide with Earth.
(A) a scale developed by astronomers rates the likelihood that a particular asteroid or comet may
(B) a scale that astronomers have developed rates how likely it is for a particular asteroid or comet to
(C) astronomers have developed a scale to rate how likely a particular asteroid or comet will be to
(D) astronomers have developed a scale for rating the likelihood that a particular asteroid or comet will
(E) astronomers have developed a scale that rates the likelihood of a particular asteroid or comet that may
Source : GMAT Official Practice Exams 3 & 4The sentence tells us that astronomers have developed a scale to rate how likely a particular asteroid/comet is to collide with Earth.
(A) a scale developed by astronomers rates the likelihood that a particular asteroid or comet may
(B) a scale that astronomers have developed rates how likely it is for a particular asteroid or comet to
The sentence starts with a present participial modifier ‘responding to the public’s fascination …’ Who responded to the public’s fascination? Astronomers. So the main clause must begin with ‘astronomers’ so that ‘responding to …’ modifies ‘astronomers.’ Else the modifier becomes dangling (in options (A) and (B)) because certainly the scale did not respond to the public. Hence options (A) and (B) are incorrect.
(C) astronomers have developed a scale to rate how likely a particular asteroid or comet will be to
Option (C) uses ‘will be’ to show likelihood and that is incorrect. We need to use the present ‘is’ because the likelihood is being calculated right now for a future event. So this is how we could write it:
…a scale to rate how likely X is to do Y (in the future).
Or
… a scale for rating the likelihood that X will do Y (in the future). (as done correctly in option (D))
We cannot say: ‘…a scale to rate how likely X will be to do Y’ because the likelihood of the future event will be calculated by the scale now. So we say how likely X is to do Y. Hence option (C) is incorrect.
(E) astronomers have developed a scale that rates the likelihood of a particular asteroid or comet that may
This option says that the scale rates the likelihood of a particular asteroid or comet. The ‘that clause’ that follows defines the asteroid/comet (the asteroid/comet that may collide with Earth). But what is meant by ‘likelihood of a particular asteroid or comet’? We need to calculate the likelihood of the asteroid/comet striking the Earth, not the likelihood of the asteroid/comet (existing?). Hence option (E) is incorrect.
Answer (D)