The correct answer is chatter.
B. fall over
The correct answer is (A) To chatter (especially childish chatter); to talk incessantly about foolish and unimportant things; to babble; to gossip; to talk in a foolish or artless way.
Prattle comes from Middle Low German pratelen.
Examples of use:
- He could only hear the sound of water as it prattled over the rocks.
- They prattled on interminably.