26.The earth travels around the sun in an oval path and one complete revolution needs

27.Variation in duration of day and night is due to 1. rotation of earth on its axis2. revolution of earth round the sun3. inclination of earth at an angle of 66 1/2 degree

28.Stars which appear single to the naked eye but are double stars when observed by a telescope, are known as

29.If there is no Sun, the colour of the sky would be

30.There is a continual daylight or summer in the Artic regions from