Hi.
Your answer would be myelin sheath.
A Petri dish (alternatively known as a Petri plate or cell-culture dish) is a shallow transparent lidded dish that biologists use to culture cells, such as bacteria, fungi or small mosses. The container is named after its inventor, German bacteriologist Julius Richard Petri. It is the most common type of culture plate.
B, the independent variable because this is the one that is purposefully changed in an experiment to test the hypothesis.
Answer:
Shadows are made by blocking light. Light rays travel from a source in straight lines. If an opaque (solid) object gets in the way, it stops light rays from traveling through it. This results in an area of darkness appearing behind the object. The dark area is called a shadow
