Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: Which set of equipment would be best to use when investigating what is found in a sample of pond water?
microscope, eye dropper, slides
Secchi disk, net, test tubes, pH meter, dissolved oxygen meter, temperature probe.