Answer:
Collection of people at a time of a place if more than thirty then such size of collection of people considered as 'population'
B. Cyclones is the correct answer because super cells are clouds, as well as wall clouds, and a vortex is another, less powerful tornado.
not sure if this is what you need.
Osteoblasts are the cells in the bone tissue that are responsible to form bone tissue itself. This is the process that allows bones to grow. To counteract this process, osteoclasts, another type of cell from the bone tissue, have the role to break down bone tissue by molecular processes - enzymatic and chemical.