Which sentence has a squinting modifier?
reading the newspaper, the train ride went by quickly.
biking to the store, jake witnessed an accident at the stoplight.
practicing football drills often is a major commitment of time.

The answer would be the third sentence. The squinting modifier is "often".

"Practicing football drills often is a major commitment of time."
    ≡ Often is a squinting modifier because it is unclear whether it pertains to "practicing football drills" frequently ("practicing football drills often"; in this case often means 'frequently') or how "practicing football drills" is usually "a major commitment of time".

Hope this helps.