The rings of Saturn must be replenished now and then by impacts on Saturn's moons or other ...

Answer to q. 1

TRUE

Answer to q. 2

FALSE

Answer to q. 3

FALSE

Answer to q. 4

Data recorded by orbiting satellites show that the southern hemisphere of Mars is a heavily cratered highland region up to 4 billion years old. The northern hemisphere is mostly a much younger lowland plain with few craters.Volcanism on Mars is dramatically evident in the Tharsis region, a highland region of volcanoes and lava flows bulging 10 km (6 mi) above the surrounding surface.All of the volcanoes on Mars are shield volcanoes, very broad mountains with gentle slopes that are produced on Earth by hot spots penetrating upward through the crust. Shield volcanoes are not related to plate tectonics; in fact, the large shield volcanoes on Mars, the largest of which is Olympus Mons, provide evidence that plate tectonics has not been significant on that planet.When the crust of a planet is strained, it may break, producing faults and rift valleys. Near the Tharsis region is a great valley, Valles Marineris, named after the Mariner 9 spacecraft that first photographed it. The valley is a block of crust that has dropped downward along parallel faults. Erosion and landslides have further modified the valley into a great canyon.

Thank you

Can you answer the others that I've posted too?

I'll take a quick look at them