The right answers are: B. and C.
This measurement technique is based on Archimedes' principle :
Any body immersed in a fluid at rest, fully wetted by it or crossing its free surface, undergoes a vertical force, directed from below upwards and opposite to the weight of the fluid volume displaced; this force is called Archimedean thrust.
For the theorem to apply, the submerged fluid and the immersed body must be at rest. It must also be possible to replace the immersed body with submerged fluid without breaking the balance, the counterexample being the stopper of a bathtub filled with water: if it is replaced by water it is clear that the tub is empty and that the fluid is no longer at rest. The theorem does not apply since we are in a case where the cap is not completely wet by the liquid and does not cross its free surface.