Which statement best describes a reaction mechanism in chemistry?

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

When balancing a chemical equation:

Ahelium balloon contains 16.9 l of helium at stp. how many atoms of helium are in the balloon