【正确答案】正确答案：plural invariables: They are (1 ) names of tools and articles of dress consisting of two equal parts: binoculars, compasses, jeans, shorts, etc. (2) some collective nouns: cattle, people, police, etc. (3) geographical names of mountain ranges, water falls, groups of islands: the Rockies , the Balkans , Niagara Falls , etc. (4) other nouns ending in -s: archives, arms, etc.