RNA interference (RNAi) technology has diverse applications, three of which are accurately represented in the options 1, 2, and 4 which forms the correct answer.

Option 1 states that RNAi is used in gene silencing therapies. This is accurate, as RNAi interferes with the expression of specific genes, hence `silencing` them.

Option 2 suggests it can be used in developing cancer treatments. This is correct because RNAi can target and silence genes that cause or promote cancerous growths.

Option 4 indicates its use in producing crop plants resistant to viral pathogens. This is true, as RNAi can target and silence the genes of viral pathogens, effectively making crops resistant against them.

Option 3, however, suggests RNAi is used in hormone replacement therapies, which is not a typical application of RNAi. This technology deals primarily with gene expression rather than hormone production or replacement, hence option 3 is not included in the answer.