Most strongly supported?

Very often. Sometimes the phrase “most strongly supported” (or ”most strongly supports”) in the question stem denotes a Must Be True question, but sometimes that phrase denotes a Strengthen question. It depends on what the question stems says is “most strongly supported.” If the question stem says to select the answer choices that is “most strongly supported” by the passage, it’s a Must Be True question. If the question stem says to select the answer choice that “most strongly supports” the conclusion in the passage, it’s a Strengthen question.