The right answer is ultrasound.
Ultrasound is an imaging technique that uses ultrasound. It is used routinely in human and veterinary medicine, but can also be used in research and industry.
Contrast ultrasound is one that uses a contrast medium. The contrast medium composed of microbubbles is injected into the bloodstream intravenously at the time of the ultrasound examination of the patient. The microbubbles of the contrast medium are highly reflective to ultrasound during ultrasound examination; thus making it possible to image the blood vascularization of the organs for diagnostic purposes.
Yes, protists have cell walls.
Protists cell walls are made of composed cellulose, protein strips , and silica
For some protists, we can even found components like pectin on the cell walls
hope this helps
IF "they" are referring to the organelle in the text as "stored in the cell" than we are talking about the Golgi apparatus, so answer D.