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.
Both chordates and invertebrates have pharyngeal pouches
The answer would be: right occiput anterior (ROA)
Presentation of fetus determines which part of their body that will be delivered first. Some presentation will have bigger surface area than others which could complicate the process of the labor. In this case, the baby back in on the right <span>between the midline and lateral surface of the abdomen, so the occipital area should be at the anterior of the pelvis.</span>
The leaves no longer have water, which means that there is little osmotic pressure which keeps it turgid.
