B
The sodium hydroxide (NaOH) solution is a basic solution, so the pH of that solution should be close to 14
then when adding hydrochloric acid (HCl) we start to neutralice the solution, meaning the pH must sift slowly to lower pH.
Assuming both solutions have similar concentration the pH shall shift form basic (above 7) to acid pH (below 7). Until now both B and D images agreed with the explanation given. To chose between them we need to remember that HCl is a very strong acid, which means that in solution will get to very acid solutions (very low pH values) which leaves only B as possible answer