Passage Summary: A scientist tagged armadillos and found most of them in the same spot months later, so he decided they don't travel to new areas very fast.

Conclusion: Armadillos generally do not move quickly into new areas.

Reasoning: Most armadillos found months later were still near the place they were originally tagged.

Analysis: The 'Gap' here is between where they were found and where they went in between. The researcher assumes that because they ended up in the same spot, they stayed there the whole time. A necessary assumption is that the armadillos found near the tagging site didn't leave and return, or that the ones not recaptured didn't all move away rapidly. Ask yourself: if the armadillos actually moved around like crazy and just happened to be back for the recapture, would the conclusion still hold? No, so the researcher must assume they stayed put.