Question 105·Hard·Form, Structure, and Sense
The staggering number of satellite images, each of which _____ meticulously cataloged before being released to the public, has enabled researchers to analyze climate patterns with unprecedented accuracy.
Which choice completes the text so that it conforms to the conventions of Standard English?
For subject–verb agreement questions, first isolate the clause containing the verb or blank. Then strip out extra phrases (such as "of satellite images" or "each of which") to find the true subject and decide if it is singular or plural. Next, match the verb’s number and tense to that subject and to the time frame implied by the sentence, ignoring nearby distracting nouns that may be closer to the blank but are not the subject.
Hints
Find what the blank is describing
Look carefully at the phrase containing the blank: it starts with "each of which" and describes the satellite images. What word in that phrase is actually the subject of the verb in the blank?
Decide on singular or plural
Ask yourself: is the subject of the blank clause referring to one thing at a time or a group of things together? Your verb must match that choice.
Check the time of the action
Is the sentence talking about a one-time event in the past, something completed, or an ongoing, general practice? Pick the verb form whose tense matches that idea.
Step-by-step Explanation
Locate the clause with the blank
Focus on the portion of the sentence around the blank: "each of which ___ meticulously cataloged before being released to the public." This is a clause describing the satellite images.
Identify the true subject of that clause
In the clause "each of which ___ meticulously cataloged," the grammatical subject is "each," not "images" or "number." "Each" is singular, so the verb that follows must also be singular.
Match the verb to number and time
Because "each" is singular, we need a singular verb form. Also, the main sentence describes something that is generally true now (satellite images are cataloged as an ongoing practice), so a present-tense verb works best. Among the choices, only D) is is singular and present, so "each of which is meticulously cataloged" is the correct completion.