I believe c is the correct answer.
At SPF 23 the sunscreen start to interfere with vitamin D.
Answer:
Environmental sanitation
Environmental sanitation encompasses the control of environmental factors that are connected to disease transmission. Subsets of this category are solid waste management, water and wastewater treatment, industrial waste treatment and noise pollution control.
Water
Water is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms. It is vital for all known forms of life, even though it provides no calories or organic nutrients
Air
Walk, bike, carpool, or take public transit.
Reduce heating needs by making your house more energy efficient. Say no to wood fire burning.Use hand-powered or battery-operated garden tools. Know before you go. Check your tire pressure. Reduce, reuse, and recycle!Be idle-free.
C. H<span>ow hard a person works to do an activity.
Intensity has to do with effort. If a person works hard than they are intense, if vise versa than they are not intense.</span>
