Question

Ned is designing an experiment to test which hand sanitizer kills the most E. coli bacteria. In order for Ned's results to be valid, what must he do?

test the first brand of hand sanitizer on E. coli bacteria, then test the second brand of hand sanitizer on a sterilized Petri dish

test each hand sanitizer on different days and at different times of the day

test the hand sanitizers first on E. coli bacteria and then on other bacterial species

test the hand sanitizers on bacterial colonies that are kept in the exact same environmental conditions, such as temperature a

Answer 1

@MysticFury @rishavraj

Answer 2

Can someone please help

Answer 3

@OregonDuck

Answer 4

The answer is D

Answer 5

It would have to be D because if you are trying to compare the brands then they have to be in the same testing area and thing