Select the most appropriate option to substitute the highlighted segment in the given sentence.
There always have been a sizeable influx of immigrants from Mexico into America.

Correct option is C

The correct substitution of the highlighted words is (c) has always been.
Explanation: The noun phrase “a sizeable influx” is singular, hence it must agree with the singular auxiliary verb “has”. Also, the correct structure for present perfect tense is “has/have + been”. Since the subject is singular, we use “has”.
Grammatical rule used: Subject-verb agreement with singular collective nouns + present perfect tense structure
Example: There has been a great response to the event.
Information Booster: Words like "amount", "influx", "quantity", though they refer to a group or total, are singular and take a singular verb.
Other Options:
· (a) No substitution required – Incorrect because “have” doesn’t agree with singular noun
· (b) were always been – Incorrect tense formation
· (d) is always being – Continuous aspect doesn’t fit the sentence structure