Which of the following lists the correct requirements for a black hole to form?
a. the star must be 10 to 28 times larger than earth's sun, and a supernova explosion must have occurred.
b. the star must be 10 to 28 times larger than earth's sun, and a supernova explosion must not have occurred.
c. the star must be 29 times larger than earth's sun, and a supernova explosion must not have occurred.
d. the star must be 29 times larger than earth's sun, and a supernova explosion must have occurred.

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.

the food storage products of chrysophytes are oils or the polysaccharide laminarin.   formerly classified as plants, the chrysophytes contain the photosynthetic pigments chlorophyll a and c all but the yellow-green algae also contain the carotenoid pigment fucoxanthin.

d. groundwater flows through the subsoil and deposits minerals.