Nitrogen in plants and soil is changed into nitrogen compounds by . nitrogen fixation
respiration
denitrification
photosynthesis

All but one describes an effect of aging on the digestive system. a) decreased acid secretion b) decreased elasticity of stomach c) capacity to resist damage decreases d) food remains in stomach for less time

In which state was more than 100 billion tons of coal mined in 2005?

Which of the follow describes a disadvantage secondary sources have compared to primary sources?