A:adaptable
B:acceptable
C:advisable
D:available
①若m=n,则|m|=|n|;②若m=﹣n,则|m|=|﹣n|;③若|﹣m|=|﹣n|,则m=﹣n;④若|﹣m|=|﹣n|,则m=n.