Option 1 -> The passage directly connects "customers barely ever walked in" with being "only disturbed five times," indicating the disturbances were from customer visits.
Option 2 -> While the shop being "another world" describes its atmosphere, it doesn't explain what caused the five disturbances.
Option 3 -> The piled-up books describe the shop's interior layout, not the reason for being disturbed.
Option 4 -> The run-down neighborhood explains WHY few customers came, but not what "disturbed" refers to.
Hence, Option 1 -> The author explicitly states that customers barely walked in because the shop was hidden away, and immediately follows this by mentioning being disturbed only five times in a year. The disturbances were the rare customer visits that interrupted the author's peaceful reading sessions with Tabby -> correct