**Core Concept**
The concept of consent in a medical or legal context is crucial, particularly when dealing with individuals who are intoxicated. In such cases, the validity of consent can be compromised due to impaired cognitive function. The Indian Penal Code (IPC) has provisions that address the issue of consent in various scenarios.

**Why the Correct Answer is Right**
Section 90 of the IPC states that when consent is given by a person who, by reason of unsoundness of mind, nonage, or intoxication, is unable to understand the nature and consequence of that to which he gives his consent, such consent is not a valid consent. This section specifically addresses the issue of consent given by a person who is intoxicated with ethanol, rendering it invalid. The term "unsoundness of mind" encompasses various conditions, including intoxication, that impair an individual's ability to provide informed consent.

**Why Each Wrong Option is Incorrect**
**Option A:** Sec 87 IPC is not directly related to the concept of consent in cases of intoxication. It deals with the issue of abetment and does not provide a specific provision for invalid consent due to intoxication.
**Option B:** Sec 92 IPC addresses consent given by an individual who is under 12 years of age, which is not relevant to the scenario described in the question.
**Option D:** Sec 89 IPC provides an exception to the general rule of abetment and does not address the issue of consent in cases of intoxication.

**Clinical Pearl / High-Yield Fact**
It is essential for medical professionals to be aware of the legal provisions governing consent in cases of intoxication, as this can have significant implications for patient care and medical liability.

**✓ Correct Answer: C. Sec 90 IPC**