If you need to do a 1:20 dilution on a culture to get acceptable plate counts, how many microliters of original sample will you add to a final volume of 16 mL

the answers would be

the first one and the second one

the answer is:  

line graphs show patterns in data with variables that change over time; whereas, circle graphs show data as parts out of a whole (such as out of 100%).

your answer is a. the enthalpy of formation for a pure element in its standard state is always positive.