Why are reflection, refraction and projection three ways a person can manipulate light

Technician a says that if a valve is open when a piston rises to the very top of a cylinder, the piston may actually strike the valve head and cause serious engine damage. technician b says if the camshaft is located in the engine block, then the engine is called an overhead valve engine, ohv engine, or an in-block camshaft. who is right? a. b only b. both a and b c. a only d. neither a nor b

How do you take a green screen out of the video while editing?

What does 21 pilots middle aged name as a band 15 years prior to them naming their band 21 pilots?