Nitrogen enters the food chain:

 a) primarily through soil-dwelling
bacteria that “fix” nitrogen by attaching it to other atoms. b) from the
atmosphere when “fixed” by the photosynthetic machinery of plants. c) when
rocks dissolved by rainwater become soil, which is then utilized for plant
growth. d) through soil erosion followed by runoff into streams and ponds. e)
through methane, produced by herbivores as a by-product of the breakdown of
plant material