The landlords are primarily violating B. Negligence.
In this context, negligence occurs when a party fails to fulfill a legal duty to act with reasonable care, resulting in harm to others. The landlords had a duty to maintain the property and address the leaking roof after multiple requests from tenants. Their failure to do so, especially leading to damage during a heavy rainstorm, constitutes negligence. Breach of duty (option A) is actually a component of the tort of negligence. Options C (fraud) and D (defamation) do not apply to the situation described.