**Core Concept**
Asherman syndrome is a condition characterized by the presence of intrauterine adhesions, leading to menstrual abnormalities and infertility. It is often caused by uterine surgery, such as dilation and curettage (D&C), or other uterine trauma. The investigation of choice for diagnosing Asherman syndrome involves assessing the uterine cavity for adhesions.

**Why the Correct Answer is Right**
The investigation of choice for Asherman syndrome is a **hysterosalpingogram (HSG)**. HSG is a radiographic examination that visualizes the uterine cavity and fallopian tubes using a contrast agent. It is particularly useful for detecting intrauterine adhesions, which may cause a characteristic "string of beads" appearance. HSG is often performed before hysteroscopy, which can be used to treat Asherman syndrome by removing adhesions.

**Why Each Wrong Option is Incorrect**
* **Option A:** Ultrasound is not the investigation of choice for Asherman syndrome, as it may not provide sufficient detail of the uterine cavity.
* **Option B:** Laparoscopy is a surgical procedure that may be used to treat Asherman syndrome, but it is not the investigation of choice for diagnosing the condition.
* **Option C:** MRI may be used to assess the uterine cavity and detect adhesions, but it is not typically the first-line investigation for Asherman syndrome.

**Clinical Pearl / High-Yield Fact**
When diagnosing Asherman syndrome, it is essential to consider the patient's medical history, including any previous uterine surgery or trauma. A high index of suspicion is necessary, as Asherman syndrome can present with non-specific symptoms such as amenorrhea or irregular menstrual bleeding.

**Correct Answer: D. Hysterosalpingogram (HSG)**