Question 102·Hard·Form, Structure, and Sense
Framed by snowcapped mountains and fed by glacial streams, _____ host more than 200 species of migratory birds each spring.
Which choice completes the text so that it conforms to the conventions of Standard English?
For questions like this, first locate the main verb that is already in the sentence and identify what the blank must be (usually a subject or part of the subject). Then, check that the option you choose: (1) is the right type of phrase (here, a noun phrase, not something with an extra main verb), (2) agrees in number with the verb, and (3) is logically described by any introductory modifier right before the comma. Read each option in the full sentence; quickly reject anything that introduces extra verbs, leaves a stray "that," or causes a subject-verb or modifier mismatch.
Hints
Figure out the role of the blank
Look at the words immediately after the blank. What part of the sentence is "host"? What kind of word or phrase must come before it for the sentence to be complete?
Connect the opening phrase to the subject
The sentence starts with "Framed by snowcapped mountains and fed by glacial streams," which must describe some thing or place. Which option makes that description logically match the thing that is doing the hosting?
Check for extra verbs or stray "that"
The main verb "host" is already given after the blank. Eliminate any option that adds another main verb before it or that ends with "that" in a way that makes the structure awkward or unclear.
Use subject-verb agreement
The verb in the sentence is "host," which goes with a plural subject (they host). Make sure the subject created by the blank is plural and matches this form of the verb.
Step-by-step Explanation
Identify what the blank needs to be
After the introductory phrase and comma, the main clause is:
"_____ host more than 200 species of migratory birds each spring."
So the blank must be a subject that can go directly in front of the verb "host". That means we’re looking for a noun or noun phrase, not something that brings in its own main verb or leaves a dangling "that."
Match the subject to the introductory modifier
The sentence begins with a participial phrase:
"Framed by snowcapped mountains and fed by glacial streams, ..."
That phrase is meant to describe the thing that hosts the birds. Logically, it makes most sense for the wetlands (a specific area within the valley) to be "framed by mountains" and "fed by glacial streams," and then to host the birds. So the subject should refer to these wetlands and be plural to agree with "host".
Eliminate choices with structural or agreement problems
Now test each option in the sentence:
-
A) "high-altitude wetlands in the valley that"
Substituting gives: "Framed by snowcapped mountains and fed by glacial streams, high-altitude wetlands in the valley that host more than 200 species..." The word "that" right before "host" unnecessarily starts a relative clause and makes the structure confusing; it suggests "the valley that host," which creates a singular/plural mismatch (valley / host) and an awkward sentence. -
C) "the valley hosts high-altitude wetlands that"
Substituting gives: "Framed by snowcapped mountains and fed by glacial streams, the valley hosts high-altitude wetlands that host more than 200 species..." This option adds a new main verb "hosts" inside the blank, even though "host" is already provided right after the blank. The result is a needlessly complicated double-"host" structure and shifts the opening description so it clearly applies to the valley, not directly to the bird-hosting wetlands. -
D) "hosting high-altitude wetlands, the valley"
Substituting gives: "Framed by snowcapped mountains and fed by glacial streams, hosting high-altitude wetlands, the valley host more than 200 species..." Here the subject "the valley" is singular but the verb is "host" (instead of "hosts"), creating a subject-verb agreement error. The piling up of participial phrases also makes the structure awkward.
Confirm the remaining, correct option
The remaining option is B) "the valley’s high-altitude wetlands".
Substitute it into the sentence:
"Framed by snowcapped mountains and fed by glacial streams, the valley’s high-altitude wetlands host more than 200 species of migratory birds each spring."
This gives a clear, grammatical sentence:
- The introductory phrase logically describes the wetlands.
- The subject "wetlands" is plural and correctly matches the verb "host".
- No extra verbs or stray "that" disrupt the structure.
Therefore, the correct answer is B) the valley’s high-altitude wetlands.