<span>b.find a meter that sounds like a metronome.</span>
Millimeters (mm) since it is a very small measurement
Knowledge because the last part that says "Im a firm believer" so that means what she thinks which is her knowledge
The sentence in which the infinitive phrase functions as the subject is the second one - To convert sunlight and energy into food is the end result of photosynthesis.
Grammarly is the one i use