When you're conducting observation qnd assessments, you must know

You should know each variable. There are two, and they are Independant and Dependant. The answer will be variable, because I don't know if you need the other two.

You must known what an independent variable is and a dependent variable and basically justa variable

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.