Problem: Stargazers across the world wait for 2020 when newly discovered very bright Neil's comet would start to pass through the inner solar system On December 21, 2020. After December 27, 2020 the comet would leave the inner solar system. Like many other enthusiasts Ken bought a telescope for the event. His friend Mike is interested in that event too, but is too busy to buy a telescope. On which date Neil's Comet would not be visible, December 21, 2020 or December 27, 2020?

A: December 27, 2020

Problem: Two friends met after 20 years. Tom had been smoking tobacco all these years and had some health problems related to that, while Randy quit smoking 25 years ago. Which friend had a lower risk of developing cancer of the mouth?

A: Randy

Problem: Two brothers Syd and Dan went to college. Syd studied plate tectonics and mantle melting. His brother Dan got to study types of soil and pedology. Which brother studied more about the influence sediments have on mantle melting?

A: Syd

Problem: Rob is an environmental scientist. He is studying the effect of insect species on environment. For his study he chose four locations, location A, location B, location C and the entire globe, which he denoted as location D. He noticed location A's loss of biodiversity is temporary , but location B's loss is permanent. Location C's loss of biodiversity yet to be determined. Would ecological restoration be helpful or not helpful for location B?

A:
not helpful