Question

across the central andes, long - term ice cores from the quelccaya ice cap ____ a continuous climate record extending back more than 1,500 years. extracted layers preserve annual snowfall patterns, and isotopic ratios are analyzed to reconstruct temperature variation. since the 2016 byrd polar climate archive update, these records have been used to calibrate regional precipitation models.
19
which choice completes the text so that it conforms to the conventions of standard english?
(answer : b)
a reveals
b reveal
c has revealed
d is revealing

Explanation:

To determine the correct verb, we analyze the subject-verb agreement. The subject "long - term ice cores" is plural. Option A "reveals" is for a singular subject. Option C "has revealed" is in the present perfect tense, and the context here is a general statement about what the ice cores do, so simple present is more appropriate. Option D "is revealing" is in the present continuous tense, which doesn't fit the general - truth - like context of the sentence. Option B "reveal" is a plural verb in the simple present tense, which agrees with the plural subject "long - term ice cores" and fits the context of stating what the ice cores do.

Answer:

B. reveal