The phrase "for the past three years" suggests an action that started in the past and is still continuing.
This requires the present perfect continuous tense: have/has + been + verb (-ing).
The correct form is:
"have been living" (present perfect continuous).
The correct sentence should be:
"They have been living here for the past three years."
Thus, the correct answer is Option A ("have been living").
Each question has a sentence that has an underlined part. Choose the option which rephrases the underlined part in the most appropriate manner in terms of grammar and usage.
In an attempt to boost their profits, many edible oil-producing companies have been engaging themselves in propaganda against commonly used oils and promoting exotic and expensive varieties of oils \(\underline{as\ more\ healthier\ options.} \)