How many days will it take to reduce 4 ci of 210po to 1 ci? how many grams of 210po does it take to produce 4 ci of activity?

Which best describes the present-day universe? opaque, expanding very slowly, stars produce heavy elements transparent, expanding at an accelerated rate, stars produce heavy elements opaque, expanding at an accelerated rate, stars produce only hydrogen and helium transparent, expanding very slowly, stars produce only hydrogen and helium