**Core Concept**
A full thickness graft involves removing the entire thickness of the skin, including the epidermis and dermis. This type of graft is ideal for covering large defects with a good cosmetic outcome. The choice of donor site for a full thickness graft depends on the availability of skin and the patient's overall health.

**Why the Correct Answer is Right**
Full thickness grafts can be obtained from sites with sufficient skin thickness and without compromising the function of the underlying organ or tissue. Sites like the buttocks, thighs, and back are commonly used due to their laxity and thickness. The scalp, however, is not an ideal donor site for full thickness grafts because of its limited skin thickness and the risk of compromising hair growth.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is correct as it is not a suitable donor site for full thickness grafts.
**Option B:** This option is incorrect as the buttocks are a common donor site for full thickness grafts.
**Option C:** This option is incorrect as the thighs are also a common donor site for full thickness grafts.
**Option D:** This option is incorrect as the back is a suitable donor site for full thickness grafts.

**Clinical Pearl / High-Yield Fact**
When selecting a donor site for a full thickness graft, it's essential to consider the patient's overall health, the availability of skin, and the risk of complications. The scalp is generally avoided due to its limited skin thickness and the risk of compromising hair growth.

**Correct Answer: A.