老大: 我有许多语法题都不明白,请求你的帮助
1.comparatively few cities in the united ststes have competing newspapers today, a major
change from 1900 () more than two newspapers.
a because then most large cities having
b when did most large cities have
c then \most large cities that had
2.()substances include various forms of silica,pumice,and emery.
a natural abrasives occur
b abrasion occurs in naatural
c naturally occurring abrasive
d a natural occurrence of abrasion
d when most large cities had