Read the dictionary entry.
foolproof (adj): 1 designed to function despite human error 2 without possibility of failure
Which sentence uses the word foolproof as described by the second definition?
The defense lawyer concluded his remarks with a foolproof argument of the defendant's innocence.
The new computers were not foolproof in the hands of untrained users.
Scientists were certain that despite being out of their control, the space probe would be foolproof.
Foolproof methods of transportation may become a reality in the near future.