When referring to an apartment block? Should it be: Block D, or block D?
You capitalize proper names. The reason 'Block' is capitalized is because you are referring to a specific block. 'The block' would not be capitalized, because - while you are referring to a particular block - you are not naming it. Similarly, if you were to say 'the D blocks,' that too would not be capitalized. While referring to specific blocks, you are not specifying which D block you are referring to.