You pick up a micro pipette that has a blue top and reads 100/1000. the window on the pipette reads from top to bottom 043. how many microliters is this?

The number on the top usually reads the maximum capacity in microlitres (1/1000) of a mL.
The display (window) shows the number of microlitres the micropipette currently contains.
Therefore the content occupies 043 microlitres.

By the way, you have a better chance posting this type of questions under the chemistry section.

The answer is Stock C