adthedaddy wrote:The seeming absence in the universe of a quantity of mass able to explain various phenomena, specifically gravitational effects, believed to be evidence for the existence of dark matter.
The original here is not an independent clause. What seems to be the main verb of the sentence, the underlined portion
believed to be, is really just the beginning of a modifier,
believed to be evidence for...
So the right answer choice will have to somehow make this sentence into an independent clause.
A) believed to be
This is wrong as discussed above.
B) is believed to be
The addition of
is in this choice make the sentence created an independent clause by changing the underlined portion from a modifier into the main verb of the sentence. There are no other issues and so this is the correct answer.
C) some believe it to be
The sentence created using this choice has two subject that don't work together. The first subject is
The absence of ... a quantity of mass able to explain various phenomena. The second is
some.
By simplifying the sentence we can make obvious the double subject issue.
The absence of mass able to explain various phenomena some believe it to be evidence.
D) some believe it is
This sentence creating using this choice also has the double subject issue. In addition there is an idiomatic issue.
believe should be followed by
it to be, rather than
it is. Notice that even if you don't know the idiom you still could have eliminated this one if you caught the double subject issue. If you are not sure of one decision point, it often helps to look for another decision point.
E) it is believed that it is
This one has a double subject issue as well. The first subject is
The absence of... The second is
it. Here is the sentence simplified. What a mess. Also,
believed that it is would be much better as
believed to be.
The absence of mass it is believed that it is evidence.
So the correct answer is
B.
