Fill in the blank with an appropriate Modal from the options:

One ________ abide by the laws.

must

The correct answer is Option (1) - must

• The sentence conveys a strong sense of obligation or necessity to follow the laws.
• "Must" is the modal verb that expresses such a compulsion or requirement, making it the most appropriate choice here.

Other options are incorrect:

• "Should" → Indicates a suggestion or recommendation, but it lacks the obligatory tone required in this context.
• "May" → Implies permission or possibility, which is inappropriate for stating a legal obligation.
• "Could" → Refers to ability or possibility in the past or conditional situations, which does not fit this context.