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?

the subject is science

So the correct answer is "Test the hand sanitizers on bacterial colonies that are kept in the exact same environmental conditions, such as temperature and light level"

Explanation:

There are several ways to make sure the results of an investigation are valid. First, you and others can try to repeat the experiment. In addition, if it is a controlled experiment, you can make sure you have a control, only one independent variable, at least one dependent variable, and constants.

For Ned's results to be valid, he needs to test the hand sanitizers on bacterial colonies that are kept in the exact same environmental conditions, such as temperature and light level.

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.