In Which generation are the parents purebred? In which generation are they hybrids?

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?

Aboy with an extra x chromosome probably has which of the following syndromes?

Which of the following is the earliest era of earth's geologic time scale? cenozoic mesozoic precambrian paleozoic