Final answer:
The mother in 'The Leap' can safely navigate her home despite being blind because she was once part of a blindfold trapeze act, which enhanced her spatial awareness and other senses.
Step-by-step explanation:
In The Leap, the main reason the narrator suggests that her mother, now blind from cataracts, can still safely negotiate her New Hampshire home is D. she was once part of a blindfold trapeze act, which developed her senses.
This unique background likely provided her with a heightened spatial awareness and the ability to navigate her surroundings without relying on sight.
The other options, such as keeping her home free of clutter or having lived there a long time, might be beneficial, but they are not cited as the main reason for her ability to move safely in her home.