If Radioactive Materials Are So Dangerous, Why Are Alpha Emitters

If radioactive materials are so dangerous, why are alpha emitters like Americium-241 readily found in the home in such things as smoke detectors?

A) radioactive materials only emit radiation when exposed to bright sunlight
B) small amounts of a radioactive material are safe to be handled
C) man made alpha emitters are much more easily handled than natural isotopes
D) gaseous alpha emitters are the only dangerous ones
E) alpha particles do not penetrate well and are absorbed by air or smoke.