Which detail best reveals the author's view that the Smithsonian is an important institution? A.
It is much larger today than it was in 1855.
B.
It is named after a British scientist.
C.
It is sometimes compared to an attic.
D.
It is described as a landmark.

D.It is described as a landmark.

Explanation:

faulty parallelism is a construction in which two or more parts of a sentence are equivalent in meaning but not grammatically similar in form.

the correct version of this faulty parallelism in the sentence is:

the hikers knew that the hike was six miles, that it usually required the entire day, and it would not be wise to start after 10: 00 a.m.

the problem is the last sentence, the first two have a basic subject+verb+object structure.

so, to give a proper balance to the structure, or better said, to give a parallel structure, we must write a basic s+v+o structure in all three sentences:

the hikers knew that the hike was six miles, that it usually required the entire day, and it would not be wise to start after 10: 00 a.m.

1. c- the tunnel project was worthwhile.

2. b- to inform about the value of the tunnel project