"plant roots compete with nitrosomonas and nitrobacter for ammonium in soil. when these bacterial groups acquire the ammonium, they turn it into"

They turn into axobacter

The speed of  sound:   sound travels  at different speeds depending on what it istraveling through. of the three mediums (gas, liquid, and solid)  sound waves travel the slowest through  gases, faster  through  liquids, and fastest  through  solids.

Ithink that b is correct but just in case wait to see if someone else answers