I'm a bit stupid, that's why I'm going to ask for help, can you be nice and help me? Thank you

Which statement is a reason to support population regulation? a) it is unethical for us to control birth control rates b) humans have the freedom to produce as many children as desired c) the gap between the rich and poor has been narrowing since 1960 d) billions more people on the earth will intensify many environmental and social problems

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

What is the subscript for oxygen in its molecular formula