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Question 6·200 Super-Hard SAT Reading Questions·Expression of Ideas

Because microearthquakes are recorded continuously, their frequency is sometimes used to rank seismic hazard where long rupture histories are unavailable. Along one section of a continental fault, instruments detect hundreds of microearthquakes each year, but satellite measurements show steady creep that releases much of the accumulated strain. An adjacent section is nearly silent; there, satellite measurements show that the fault is locked, and trench records document repeated large ruptures. Neither section’s instrumental record spans a complete rupture cycle, leaving any link between changes in event rate and the timing of a rupture unresolved. ______ the contrast between the creeping, active section and the locked, quiet one rules out treating event counts alone as a direct measure of stored strain across sections.

Which choice completes the text with the most logical transition?