It's the crystal <span>quartz.</span>
I can't see the problem for number 18 write it out and I can help you!
They reproduce using spores not seeds
phytoplankton falls on the first trophic level which is are "primary producers", it is because even smallest to smallest creatures like zooplankton feed on phytoplankton.
The correct answer is: c. Mitochondria and d. Rough ER
Protein disulfide bonds are the links between the sulfur atoms of two cysteine amino acids of the protein and these bonds are part of the secondary and tertiary structure of proteins. Formation of disulfide bonds is very important for the folding and stability of some proteins. Disulfide bonds are mostly found in secretory proteins and lysosomal proteins because of their unstable state in cytosol.