Assume that the contaminated water is to be used for drinking. Using principles of hydraulics, calculate the diameter of a cast iron pipe needed to obtain steady uniform gravity flow of about 0.04 m3/sec given a grading of 0.5% slope.

The answer for #3 is c but i don't know why

Which ocean zone has the most abundant primary producer and why a) the abyssopelagic zone ,du to the absence of light and cold water temperatureb) the bathypelagic zone, due to the absence of light and cold water temperaturec) the mesopelagic zone ,due to uts high light availability and warm water temperature d) the epipelagic zone, due to its high light availability and warm water temperature

How does the viscosity of magma change as magma cools?