判断题 The division of English into Old English， Middle English， and Modern English is nonconventional and not arbitrary.

判断题 An important difference between presupposition and entailment is that presupposition，unlike entailment，is not vulnerable to negation. That is to say, if a sentence is negated, the original presupposition is still true.

判断题 Linguistic forms having the same sense may have different references in different situations while linguistic forms with the same reference always have the same sense.