Question

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?
foolproof methods of transportation may become a reality in the near future.
the defense lawyer concluded his remarks with a foolproof argument of the defendant’s innocence.
scientists were certain that despite being out of their control, the space probe would be foolproof.
the new computers were not foolproof in the hands of untrained users.

Explanation:

The second definition of "foolproof" means "without possibility of failure". We analyze each option:

1. "Foolproof methods of transportation may become a reality..." uses the term to mean resistant to human error/failure, but it's a hypothetical future concept, not a stated guaranteed failure-free thing.
2. "A foolproof argument of the defendant's innocence" means the argument cannot fail to prove innocence, matching the "without possibility of failure" definition.
3. "the space probe would be foolproof" refers to functioning despite being out of control, aligning more with the first definition (functioning despite human/control error).
4. "not foolproof in the hands of untrained users" directly references failing due to untrained people, matching the first definition's context of human error.

Answer:

The defense lawyer concluded his remarks with a foolproof argument of the defendant's innocence.