A25 ml sample of 0.100 m hno3 completely reacts with naoh according to this equation:

hno3(aq) + naoh (aq) ⟶ nano3(aq) + h2o(l)

how many moles of hno3 are in the sample?
⇒ 0.0025 mol hno3

what volume of 0.0500 m naoh solution is required to completely react with the hno3?

if someone could teach me how to do this, it would be awesome

It is a good thing that you already have answered the first question. Now, moving on to the second question, there exist an equation for the neutralization of acid by a base that is shown below,
                                          M₁V₁ = M₂V₂
Now, all the variables in the equation are given except for our unknown which is the V₂. Substituting the known values from the given above,
                                       (0.1 M)(25 mL) = (0.05 M)(V₂)
The value of V₂ from the equation above is 50 mL. Therefore, 50 mL of 0.05 M NaOH solution will be needed to completely react with HNO3. 

Ithink the answer is b.