**Core Concept**
Benzodiazepines are a class of sedative-hypnotic drugs used to treat anxiety, insomnia, seizures, and muscle spasms. They act on the GABA_A receptor, enhancing the effect of the neurotransmitter GABA, leading to a calming effect on the nervous system.

**Why the Correct Answer is Right**
The shortest-acting benzodiazepine is Triazolam, with a half-life of approximately 1.5 to 5.5 hours. This allows for rapid onset and offset of action, making it suitable for short-term treatment of insomnia. Triazolam binds to the benzodiazepine site of the GABA_A receptor, increasing the frequency of chloride channel opening and enhancing the inhibitory effects of GABA.

**Why Each Wrong Option is Incorrect**
**Option A:** Lorazepam - Although lorazepam has a relatively short half-life, it is not the shortest-acting benzodiazepine. Its active metabolite, lorazepam glucuronide, contributes to its longer duration of action.
**Option B:** Midazolam - Midazolam is a short-acting benzodiazepine but is primarily used for sedation and anxiolysis in medical procedures, rather than for the treatment of insomnia.
**Option C:** Alprazolam - Alprazolam has a moderate half-life and is commonly used to treat generalized anxiety disorder, making it less suitable as a short-acting benzodiazepine for insomnia.

**Clinical Pearl / High-Yield Fact**
When choosing a benzodiazepine for short-term use, consider the desired duration of action and potential for dependence. The shorter the half-life, the lower the risk of accumulation and dependence.

**Correct Answer:** B. Midazolam.