Ngữ pháp toefl itp-Mạo từ a và an P4

Jim Thorpe, a football, track, and baseball stars from Pennsylvania, is considered by many to be the greatest all-around athlete of modern times

Some cities have a fire regulations that requires people to put smoke detectors in their houses.

A time zone is a slightly irregular north-south belts that extends from pole to pole.

A significant proportions of the plants and animals of Hawaii exists nowhere else in the World

A electric current can consist of charges that are positive, negative, or both.