The correct answer is a - silicon dioxide.
Diatoms are single celled algae. They have a silica - based cell wall called a frustule, which gives each diatom a particular shape.
Diatoms exist as separate single cells although some may be found in groups or colonies. The ones found in colonies create very pretty forms: leaf shaped, oval , star and even like a period.
Outer shells of diatoms are quite valuable. They are used in industry in the manufacture of toothpaste to give it grit.
The most constant temperature is found in tropical rainforest.
Tropical rainforests are found near the equator and have temperatures between 20°C and 25°C year-round. There is no dry season in tropical rainforests, all months have an average precipitation and receive about 250 cm of rainfall per year. Tropical forests are classified by the amount of rainfall received each year.
The organelles that perform roles equivalent to circulatory are ribosomes,endoplasmic reticulum,and the golgi body
