1). Have been2). Have3). Has4). Has been

1.	1). Have been2). Have3). Has4). Has been
Answer» The BLANK must contain an auxiliary verb, as the verb PRESENT in the sentence is in its past participle form. The chosen word must also reflect the tense, which is perfect tense, as the verb indicates. The NOUN in the sentence, 'they' is a plural, which means the appropriate perfect tense auxiliary verb would be 'have' and not the singular 'has'. Therefore, the correct answer is option 2.

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