Selenium-83 has a half-life of 25 minutes. How many minutes would it take for a 12.0 mg sample to decay and have only 0.375 mg of it remain?

Iknow #2 is d. i just need to know why

Which traits do human embryos have that link them to a common ancestor with fish and reptiles? a. scales and tail b. gill slits and scales c. tail and gill slits d. hair and tail

In chemistry, the type of an atom (what element it is) is determined by: a) the number of protons it contains in its nucleus. b) the number of neutrons it contains in its nucleus. c) the number of protons it has in a cloud around the nucleus. d) the number of neutrons it has in a cloud around the nucleus. e) the number of electrons it exchanges with its neighbors.