After performing a dilution calculation, you determine you need 25.0 milliliters of an aqueous stock solution to make 100.0 milliliters of a new solution. how would this be prepared?

To solve this we use the equation, 

M1V1 = M2V2

where M1 is the concentration of the stock solution, V1 is the volume of the stock solution, M2 is the concentration of the new solution and V2 is its volume. 

We prepare the solution by measuring 25 mL of the stock solution in a graduated cylinder or by using a pipette. Then, put the stock solution in a 100mL of volumetric flask. Dilute it by adding distilled water up to the 100mL mark in the flask. It should be noted that the lower meniscus of the solution should be the point where you observe the volume. 

they are all solids.

i think it's letter a.