Why do we need to start using more renewable energy sources and rely less on on fossil fuels

The use of logic making empirical observations and performing dissections were all part of the scientific studies by

The oxidizing agent our bodies use to obtain energy from food is oxygen (from the air). if you breathe 15 times a minute (at rest), taking in and exhaling 0.5 l of air with each breath, what volume of air do you breathe each day? air is 21% oxygen by volume. what volume of oxygen do you breathe each day?

Which number represents a basic ph, 4 or 9? numerical answers expected! answer for blank 1: i'll give