RNA Splicing Provides an Opportunity for Regulating Gene Expression Because

RNA splicing provides an opportunity for regulating gene expression because:

A) the same exons may be spliced together in different sequences to produce different proteins from the same primary transcript.
B) the same introns may be spliced together in different sequences to produce different proteins from the same primary transcript.
C) a spliceosome in one cell can "see" as an intron what another spliceosome in another cell "sees" as an exon, allowing different proteins to be produced from the same primary transcript.
D) methylation of spliceosomes controls how rapidly primary transcripts are processed and sent to the cytoplasm.
E) methylation of the poly(A) tail controls how rapidly the primary transcript can be broken up and spliced back together again.