Physical change as no new substance is created
I think it would be D. because your hypothesis wasn't correct.
Very powerful microscopes were needed before cells could be observed in detail
Landslide is a general term referring to all types of surface movement, like avalanches involving the mass movement downhill of soil, rock, or snow under the action of gravity. These can be dangerous to human life.
Mudslides are caused unusually heavy rain or sudden thaw. they consist of mostly mud and water with fragments of rock and other debris. They're capable of moving house off of their foundations and can bury a place within minutes.