Final answer:
The duration of the block increases as the mass of the local anesthetic increases.
Step-by-step explanation:
As the mass of the local anesthetic increases, the duration of the block also increases. Local anesthetics work by temporarily blocking nerve conduction in the area where they are applied. The larger the mass or amount of the anesthetic, the longer it will be effective in blocking nerve signals. This means that the sensory and motor paralysis caused by the anesthetic will last for a longer period of time.