Nitrogen-fixing bacteria live in protective nodules (bumps) on the roots of some plants. these bacteria are able to convert gaseous nitrogen from the air into a form of nitrogen that the plants can use. which type of relationship is this? a. mutualism b. predation c. commensalism d. parasitism i think it is a or b

I believe it is A because the plant is offering protection while the bacteria is converting it in to nitrogen that the plant can use!

The internal energy of the system we can term it as total potential energy and kinetic energy. energy flows out of the surrounding from the system then we can say that the internal energy of the final state is lower than its initials. the sign of  δesystem is negative.δesystem = efinal - einitial=-ve  efinal  ∠einitial.