Net primary production (npp) refers to…
a. the total amount of organic matter fixed through photosynthesis
b. the total amount of organic matter fixed through photosynthesis minus that lost through respiration
c. the total amount of organic matter fixed through photosynthesis minus that lost through herbivory
d. the total amount of organic matter fixed through photosynthesis minus that lost by chance
e. the total amount of data on the world wide web

b. the total amount of organic matter fixed through photosynthesis minus that lost through respiration

Explanation:

The activity of an ecosystem can be assessed by gross primary productivity, which corresponds to the total organic matter produced in grams over a period of time in a given environmental area.  Discounting from this total the amount of organic matter consumed by the organisms, during this period, in respiration, we have the net primary productivity.

For this reason, we can conclude that net primary production corresponds to the total amount of organic matter fixed through photosynthesis minus that lost by plant respiration.

photosynthesis makes the glucose that is used in cellular respiration to make atp. the glucose is then turned back into carbon dioxide, which is used in photosynthesis. while water is broken down to form oxygen during photosynthesis, in cellular respiration oxygen is combined with hydrogen to form water.