Ngữ pháp toefl itp-Mạo từ a và an P2

Physiologically, the period of adolescence is marked by active growth, especially in the skeletal and muscular systems and in a certain vascular tissues

Oscillation is a electronic function that changes direct current to the signal of desired frequency.

The Sun’s energy is generated deep in the solar core by the synthesis of helium from hydrogen through a sequences of thermonuclear fusion reactions.

A coral reef, a intricate aquatic community of plants and animals, is found only in warm, shallow, sunlit seas

Long before his death, John Dewey saw his philosophy have a profound influences on education and thought in the United States and elsewhere.