I think the key is “what does this (observation – “blockage”) show”.
(A) Water has a definite volume – the water is blocked by the ice doesn’t show this. -OUT
(B) Ice cube cannot be compressed…. – Conceptually true but not sure of the relevance to the observation on first instance. Will revisit again. (see below)
(C) Water occupies space in the glass…. [totally irrelevant to the observation.] – OUT
(D) Ice cube… definite shape… cannot fit through. [Yes, it is the main reason for the “blockage”] -IN
By elimination, A and C are out, left option(2): B and D only.
Maybe in some sense, B may be a plausible answer. Since, if ice cube can be compressed, there will be less “blockage”. So answer is option (2) to me.