It is not possible to select an answer since information is missing, but we can start by discarding the first option, since 100 ul refers to volume measurement, it is not a concentration measurement that must contain mass and volume in its units, such as mg/L , mol/L or something similar.
For clarity 1uL equals 0.001mL.
Now, we are given two terms that make up a solution. Remember that a solution is the mixture of two or more compounds that form a single phase, that is, it is a homogeneous mixture.
The solvent is the one that is in greater proportion and is generally a liquid. The solute is in smaller proportion and it dissolves in the solvent, it is generally solid but it can also be a liquid or gas.
Now, solution dilution is when we have an initial solution with an initial solute concentration. Dilution refers to adding more solvent to the solution, thus the concentration of the solute decreases.
As I say, you can not choose an answer since information is missing. That can be the volume of the solvent, or the volume of the solute in case it is liquid, that is, the volume of the solution.