Choice (A) uses the phrase "because of," which always introduces a noun (in this case, "asking," a gerund, a verb functioning as a noun). Typically, using "because of" is awkward and less clear, and that's true in this case.
In choice (B), the initial modifying phrase, "Having repeatedly asked for better safety equipment," correctly modifies "the construction workers." The verb tense is also correct; they did the repeated asking before they went on strike, so "having repeatedly asked" is accurate. Choice (B) is clear and correct.
In choice (C), the word "thus," like "finally," is an adverb, not a conjunction, and it's being used as a conjunction. Moreover, the phrase starting with "refusing" is a modifying phrase, not an independent clause. Accordingly, they don't work well together; "thus" is used to introduce an independent clause. Finally, the intended emphasis of the sentence is on the latter clause, but in choice (C) the emphasis rests with the independent clause, the first part, whereas. We can eliminate choice (C), and choice (D), on similar grounds.
Choice (E) is awkward and obscures the intended meaning. It's phrased as if to hide or make unclear who did the "asking," since the passive voice is used, and that's not the intended meaning of the sentence. We can eliminate choice (E).
The correct answer is (B).