What is used to measure the cardiovascular system is receiving that most benefit from exercise without working too hard

Target heart rate is the answer because target heart rate is to be maintained during exercise to ensure the best cardiovascular function

The target heart rate because that is whats used while exercising.

You did not show us the image of the burger, but i shall try to answer as best i can.  when purchasing food, always consider the ingredients as well as the person who prepared it. consider if they were hygienic people or not, in case the burger was infected with bacteria. no mortal should place an infected burger into their mouth.