What causes clouds of dust and gas to form a protostar?
(1) magnetism (3) expansion of matter
(2) gravitational attraction (4) cosmic background radiation

the following sets of characteristics describe what we know about the outer plants is c. rocky surface, closet to the sun and larger in size

true. earthquakes are felt whenever there is a slip around a fault in the rocks below the earth. this reorientation of faults create sesmic waves and is known as earthquake, the severity of which is measured in richter scale. these are more prominent in hilly regions as the rocks usually form faults to balance the pressures on it.