The drugs were innocuous and had no side effect.

The correct answer is B. harmless.

Innocuous means not harmful or dangerous. The drugs were innocuous and had no side effect, meaning that they were safe to take and did not cause any negative effects.

The other options are incorrect because:

• Effective means producing the desired result. The drugs were effective in treating the patient’s condition.
• Imported means brought in from another country. The drugs were not imported, they were made in the country where the patient lived.
• Discovered means found or learned about. The drugs were not discovered, they were already known to exist.