Answer: Cardio.
Explanation: Cardio is the exercise type that burns the most calories. Running, for example, is the top exercise of calorie-burn.
The answer is b are expensive
HIV crossed from chimps to humans in the 1920's in what is now the Democratic Republic of Congo. This was probably as a result of chimps carrying the Simian Immunodeficiency Virus (SIV), a virus closely related to HIV, being hunted and eaten by people living in the area.
