The smallest blood vessels that connect arteries and veins, and allow blood to pick up and drop off substances with surrounding cells.

answer: wheres the options

explanation:

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.

yes, because even though a theory has a  lot of evidence to support it, it is not always true