Tìm lỗi sai
1.The Post Office, (that is) a retail company in the United Kingdon; (formerly part) of (the postal service) Royal Mail,
(became) a separate entity in 1981
2. In 1823, the Post office (used) steamboats (to carry) mails and parcels (between) post towns (which) no roads existed
3. On February 22, 1921, (when) mail (was flown) both day (and) night (for the first time)
4. In 1930, (more than) 10000 trains (which were used) (for moving) the mail into every city, town, and village (in the United States)
5. (When) railroad mail service began, mostly letters (were sorted) on the trains, (which) (were not equipping) to distribute other kinds of mail
1. that is
2. which
3. when
4. which were used
5. were not equipping