Im an experiment , the group that is exposed to the variable to be tested is called the ?

The correct answer is the experimental group.  

A group in an experiment, which receives the variable being tested is known as an experimental group. One variable is being examined at a time. The experimental group is compared with a control group that does not get the test variable. In this manner, experimental groups are used to determine the answers in an experiment.  

no, the red giant is the hottest with 2.00.000.000 degrees celsius. while the white dwarf only 25,000 degrees celsius.