Which of the Following Might Be Considered a Viable Application

Multiple Choice

Which of the following might be considered a viable application of a radioactive tracer?

A) adding a stream of radioisotopes to wastewater to examine where pollution goes when it flows into the ocean
B) placing radioactive sources around a room to trace the location of people as they move through the room
C) embedding a radioactive plug in a valuable necklace so that its location can be determined using a Geiger counter
D) all of the above
E) none of the above