**Core Concept**
The underlying principle in this question is the relationship between denture irritation and oral mucosal lesions. Denture irritation can cause chronic inflammation and irritation of the oral mucosa, leading to the development of white patches, also known as pseudomembranous candidiasis or oral thrush.

**Why the Correct Answer is Right**
The correct answer is **C. Asceaining that denture is fitted properly** because improper denture fitting can cause chronic friction and irritation of the oral mucosa, leading to the development of white patches. This is a common condition known as denture-induced stomatitis. The fitting of the denture should be checked to ensure that it is not causing excessive friction or pressure on the oral mucosa, which can lead to inflammation and irritation.

**Why Each Wrong Option is Incorrect**
**Option A:** Low dose radiotherapy is not a suitable treatment for denture-induced stomatitis. Radiotherapy is typically used to treat malignant conditions, and it is not indicated for this condition.

**Option B:** Biopsy of all the tissues is not necessary in this case. A biopsy may be indicated if there is suspicion of a malignant condition, but in this case, the clinical presentation is consistent with denture-induced stomatitis.

**Option D:** Antibiotics are not indicated for denture-induced stomatitis. This condition is caused by chronic inflammation and irritation, rather than a bacterial infection.

**Clinical Pearl / High-Yield Fact**
It is essential to note that denture-induced stomatitis can be prevented by ensuring proper denture fitting, cleaning, and maintenance. Regular dental check-ups can help identify and address any issues related to denture fitting, reducing the risk of developing this condition.

**Correct Answer Line**
✓ Correct Answer: C. Asceaining that denture is fitted properly