What are tiny blood vessels that has walls thin enough for carbon dioxide and oxygen to be exchanged

Which practice is harmful to the land? a. using animal waste as fertilizer b. composting with peels from commercial fruit c. throwing paint cans in the garbage d. cutting the lawn with a gas-powered mower

Dark clothing enables sweat to be evaporated on the skin's surface very quickly. loose light tight

Why is it important to know first aid/ cpr/ aed?