Concept:The sentence requires a logical conclusion based on evidence, using the correct modal verb of probability.
Explanation:The phrase “Since you have been touring all day” sets up a clear cause-and-effect situation.
Touring all day is a tiring activity, so the most natural conclusion is that the person is tired now.
The modal “must” is used to express a strong probability when there is good evidence.
Option 1, “you must be tired”, correctly conveys this strong logical deduction.
Option 2, “you ought to have been tired”, is grammatically wrong because “ought to” expresses advisability, not probability, and the tense is mismatched.
Option 3, “you could had been tired”, is incorrect – “could” requires “have” (not “had”) and still does not fit the logical certainty.
Option 4, “you might not be tired”, is illogical because it suggests a weak possibility that contradicts the clear evidence of a long day of touring.
Thus, only option 1 forms a grammatically and logically correct sentence.
Answer:Option A: you must be tired.