**Core Concept**
The optimum floor space recommended per adult person in a house is a measure of minimum living standards, taking into account factors such as personal space, comfort, and health. This concept is related to the field of environmental health and public health engineering.

**Why the Correct Answer is Right**
The recommended floor space per adult person is typically around 7-10 square meters (75-107 square feet). This is because a larger floor space per person allows for better ventilation, reduced overcrowding, and improved mental health. The World Health Organization (WHO) and other health organizations have established guidelines for minimum living space to ensure a healthy and dignified living environment. The floor space requirement also considers the need for personal space, furniture, and movement within the dwelling.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is too low, leading to overcrowding and potential health issues.
**Option B:** This option is incorrect because it is too high, resulting in unnecessary resource consumption and environmental impact.
**Option C:** This option is incorrect because it is not a commonly accepted standard for floor space per person.

**Clinical Pearl / High-Yield Fact**
A commonly accepted rule of thumb is that each person should have at least 7-10 square meters (75-107 square feet) of floor space in a dwelling to ensure a healthy and comfortable living environment.

**Correct Answer: D. 7-10 square meters**