Question

how migratory shorebirds recalibrate their navigation after severe storms ___ unclear, despite satellite - tracking data collected across the yellow sea since 2016. numerous attempts to model post - storm route correction—including analyses of wind displacement, magnetic orientation, and altered stopover timing—have produced conflicting results, suggesting that multiple overlapping cues rather than a single mechanism guide recovery in long - distance migration.
17 □ mark for review
which choice completes the text so that it conforms to the conventions of standard english?
(a) remain
(b) remains
(c) have remained
(d) remained

Explanation:

The subject of the sentence is the clause "How migratory shorebirds recalibrate their navigation after severe storms", which functions as a singular subject. So, the verb should agree with a singular subject. "Remains" is the singular form of the verb "remain" in the present tense, which fits the context of the text (talking about a current state of being unclear). "Remain" is plural, "have remained" is plural and in present perfect, and "remained" is past tense, none of which fit the subject and the context here.

Answer:

B. remains