Can someone please please please please please help me thank you

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

Which of these is most responsible for differences between the twentieth century to the twenty-first century?

What is the digital revolution and how did it change society? what are the benefits of digital media?