Which option allows users to graph historical spreads?

Choosing RVM as the option that allows users to graph historical spreads is correct because RVM stands for "Relative Value Map," a tool on Bloomberg that facilitates the visual comparison of spreads over time. This function helps users observe trends, analyze shifts in relative pricing, and examine potential trading opportunities by looking at historical data.

The other options do not specifically focus on graphing historical spreads. For instance, YCRV (Yield Curve) is primarily used to display yield curves for various fixed-income securities, while RVS (Relative Value Spread) is more concerned with comparing current valuation rather than providing a historical graph. FWCV (Fixed Income Composite View) aggregates bond information and analytics but does not specialize in graphing historical spread data. Thus, RVM is the targeted tool for this specific analytical need.