A mild haemorrhage will cause stroke volume to shift from point X to point:

**Core Concept**
The Frank-Starling mechanism describes the relationship between stroke volume (SV) and preload, where an increase in ventricular preload results in an increase in stroke volume. This is due to the stretch-activated mechanisms of the cardiac myocytes, leading to increased contractility.

**Why the Correct Answer is Right**
A mild haemorrhage would lead to a decrease in venous return, causing a decrease in preload. According to the Frank-Starling mechanism, a decrease in preload would result in a decrease in stroke volume. The new equilibrium point would be at a lower stroke volume. This is because the ventricles receive less blood, resulting in a lower preload and a lower stroke volume.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because a mild haemorrhage would not cause a significant increase in stroke volume. The Frank-Starling mechanism dictates that an increase in preload would result in an increase in stroke volume, not a decrease.
**Option B:** This option is incorrect because a mild haemorrhage would not cause a decrease in stroke volume to the point where it would shift to a completely new point on the cardiac function curve. The new equilibrium point would be at a lower stroke volume, not at a completely different point.
**Option C:** This option is incorrect because a mild haemorrhage would not cause a significant increase in stroke volume. The Frank-Starling mechanism dictates that an increase in preload would result in an increase in stroke volume, not a decrease.

**Clinical Pearl / High-Yield Fact**
Remember the Frank-Starling mechanism: an increase in ventricular preload results in an increase in stroke volume, and a decrease in ventricular preload results in a decrease in stroke volume.

**Correct Answer: B. Lower stroke volume**