Cave

  A cave or cavern is a hollow place in the ground,^[1][2] especially a natural underground space large enough for a human to enter. Caves form naturally by the weathering of rock and often extend deep underground. The word cave can also refer to much smaller openings such as sea caves, rock shelters, and grottos. ...อ่านเพิ่มเติม

Deserts

  Deserts cover about one fifth of the Earth’s surface and occur where rainfall is less than 50 cm/year. Although most deserts, such as the Sahara of North Africa and the deserts of the southwestern U.S. ..อ่านเพิ่มเติม

Paper

  Paper is a thin material produced by pressing together moist fibres of cellulose pulp derived from wood, rags or grasses, and drying them into flexible sheets.It is a versatile material with...อ่านเพิ่มเติม