Which labels best complete the flow chart?
OX: Producers undergo photosynthesis.
Y: Nitrogen compounds are released into the air
O X: Nitrogen compounds are released into the air
Y Producers undergo photosynthesis.
O X: Free nitrogen is in the atmosphere.
Y. Producers absorb nitrogen compounds through their
roots
X: Producers absorb nitrogen compounds through their
roots
Y: Free nitrogen is in the atmosphere.

The labels that best complete the flow chart are:

X: Free nitrogen is in the atmosphere and Y: Producers captivate components of nitrogen via their roots.

Explanation:

Soil comprises nitrogen, it is taken up by the plants accompanied by other minerals in the process of taking water from the soil. The presence of nitrogen in the soil takes place by the process of decomposition of decaying and dead substances. The process of decomposition dissociates nitrogen and discharges it within the soil. This nitrogen is eventually taken up by the plants.  

Label X shows that in the air presence of nitrogen takes place in its free state, as it is one of the gases found in abundance in the atmosphere of the Earth.  

it provides an alternative energy pathway for the reaction to proceed.

a catalyst is a substance that speeds up the rate of a chemical reaction but is not consumed during the course of the reaction.

catalysts increase the rate of reaction without being used up. they do this by lowering the activation energy needed. with a catalyst, more collisions result in a reaction, so the rate of reaction increases. different reactions need different catalysts.

a catalyst works by providing an alternative reaction pathway to the reaction product. the rate of the reaction is increased as this alternative route has a lower activation energy than the reaction route not mediated by the catalyst.