Answer asap:
what is the general idea behind the use of small amounts of radioactive tracers in medicine?
they can be used to identify an unknown sample. < i don't think its this one.
they kill cancer cells.
they allow doctors to detect problem areas.

his week a heat wave will be hitting, and most of the country will be experiencing temperatures above average for july. due to humidity, the temperature outside can feel even warmer than it actually is. this adjusted temperature, often referred to as the “feels like” temperature is called the heat index. the chart shows the heat index, which is calculated based on temperature and relative humidity. use this chart to answer the following questions.  

which ever one is showing doing the same exercise in time intervals such as 30 seconds or a minute several times.