Question

question 9 (1 point)
most biogenic sediments consist of tiny shells called microfossils that are made of what two substances?
sio2 and co2
sio2 and mno2
caco3 and fe3o4
caco3 and sio2
caco3 and mno2

Explanation:

Biogenic sediments' micro - fossils are commonly made of calcium carbonate ($CaCO_3$) and silica ($SiO_2$). Calcium carbonate is from organisms like foraminifera and coccolithophores, and silica from diatoms and radiolaria.

Answer:

D. $CaCO_3$ and $SiO_2$