Modern communications satellites use a variety of orbits, including ( ). A: geostationary orbits B: Molniya orbits C: elliptical orbits D: low (Polar and non-polar) earth orbits

_____ is covered with heavy snow. A: The earth’s surface B: The surface of earth C: The surface earth D: The earth surface

The earth _______ round the sun, and the moon _________ round the earth

Mercury freezes if it is cooled to＿. A: a too low temperature B: too low temperature C: a low too temperature D: too low a temperature

The champion boxer fought bravely to defend his title, but was finally by a knockout blow. A: laid low B: lay low C: lie low D: lying low

______ is the center of our planetary system was a difficult concept to grasp in the Middle Ages.(1.0) A: It is the sun and not the earth B: Being the sun and not the earth C: The sun and not the earth D: That the sun and not the earth

The purpose of Earth Day is ______. A: to help people memorize the earth B: to help people to learn how to protect the earth C: to unite all the people on the earth D: all of the above

One day on the moon is ______. A: two Earth week long B: two Earth weeks long C: two Earth weeks longer D: two Earth weeks length

____isthe center of our planetary system was considered as heresy by the church in the Middle Ages. A: It is the sun and not the earth B: That the sun and not the earth C: Being the sun and not the earth D: The sun and not the earth

digitalRead(KEY)==LOW语句中lOW表示（ ）。