Doctors use the radioactive isotope chromium-51 to label red blood cells in the human body. Chromium-51 gives off relatively alpha particles that can be stopped by . A) energetic; lead
B) weak; a sheet of paper.
C) weak; a thin sheet of copper.
D) energetic; a thick sheet of copper.

It is believed that europa, one of jupiter’s moons has an ocean beneath its surface. based on how earth’s oceans and atmosphere are believed to have formed, what can be said about europa’s supposed ocean? the arrival of in the early days of europa’s existence could have formed its ocean. it is likely that the water experienced , similar to earth. it is also possible that this water is retained beneath europa’s surface and in its atmosphere due to europa’s .