Question 3
Why does the graduation mark of a volumetric flask sit on the narrow neck rather than on the wide body?
The right answer is the one marked above.
So a small error in reading the level is a small error in volume. In a narrow tube a misjudgement of a millimetre is a tiny volume. On a wide body the same misjudgement would be several millilitres out.
This is why a beaker will not do for the job. Its graduations are approximate and its sides are wide, which throws away the accuracy the careful weighing was for.