Topic: Adverb (ক্রিয়াবিশেষণ),

Best Answer Explained in Below-:

In the sentence "The doctor ___ checked the patient and found only minor problems," the context implies a certain level of attention and diligence in the doctor's examination. The correct choice, "thoroughly," aligns with the expectation that a doctor would perform a comprehensive assessment to ensure no significant issues are overlooked.

When a doctor checks a patient thoroughly, it indicates meticulousness and a deep investigation into the patient's condition. This level of scrutiny is necessary in the medical field to ensure accurate diagnoses and effective treatment.

In contrast, the other options do not fit the context as well:

- **Casually** suggests a lack of seriousness or attention, which contradicts the responsibility a doctor has regarding a patient's health.
- **Reluctantly** implies hesitance or unwillingness, again not aligning with professional medical practice.
- **Thoughtfully** could suggest consideration, but it doesn’t convey the systematic and detailed approach implied by a medical examination.

Thus, "thoroughly" is the most appropriate choice as it accurately reflects the seriousness and professionalism expected from a doctor when examining a patient.