The correct option is B R T S P Q
The type 3 conditional refers to an impossible condition in the past and its probable result in the past. These sentences are truly hypothetical and unreal, because it is now too late for the condition or its result to exist. There is always some implication of regret with type 3 conditional sentences. The reality is the opposite of, or contrary to, what the sentence expresses. In type 3 conditional sentences, the time is the past and the situation is hypothetical. The sentences in this case start with "had" to express condition, like "had I known". The full sentence is " Had I known the nature of the job earlier, I would not have accepted it". Hence, Option B is correct. The rest of the options do not express this condition, hence incorrect.