In a redox reaction electrons are lost and gained in equal numbers. The species that is oxidized gives electrons to the species that is reduced. I hope this helps. Let me know if anything is unclear.
He could go at any of the first 3 times because he won't get back if he goes on the last. We need more information to help answer it.
Answer:
metals
Explanation:
Approximately three-quarters of all known chemical elements are metals. The most abundant varieties in the Earth's crust are aluminum,... Gold (Au), chemical element, a dense lustrous yellow precious metal of Group 11 (Ib), Period 6, of the periodic table.

How can telescopes aid visualizing the electromagnetic spectrum?what is the “best place” for telescopes “to detect most radiation” and why?

Astronomers use telescopes that detect different parts of the electromagnetic spectrum. Each type of telescope can only detect one part of the electromagnetic spectrum. There are radio telescopes, infrared telescopes, optical (visible light) telescopes and so on.
The best place to detect most radiation is above the blocking atmosphere, so some telescopes are put in orbit around the Earth. Even visible light is distorted by the atmosphere, so clearer pictures can be got from orbiting telescopes.
Fiber aids in waste remover