What is hydrogen a mixture ,element, or compund?

Match the mixture with the substance// i really need on this guys (it’s a pic btw)

Stage in which a typical star has completely stopped fusion

The graph indicates the running route for tobias. which best describes his run? from time 0 to 6, he went fast and then slowed down. from time 6 to 10, he was at his slowest. from time 12 to 14, he went very slow. from time 14 to 18, he went toward the starting point.