15 minutes later she resigned to the fact that she could be in there all day long so she started looking around . That 's when she noticed the 6.5-inch gap above and below the otherwise impenetrable door , and a bulb went off inside her dome .

Question: Why is the 6.5 inch gap at the bottom of the door significant ?
Answer: None of the above choices .The gap " might " be large enough for her to squeeze through .The gap might be large enough for her to read her book by the light .The gap is large enough to fit her pet bird through .