**Core Concept**
A normal partogram is a graphical representation of the progress of labor in a pregnant woman. It is used to assess the progress of labor, identify any potential complications, and make informed decisions regarding the management of labor. The partogram typically includes several key parameters, including cervical dilatation, fetal head descent, and the presence of any complications.

**Why the Correct Answer is Right**
In a normal partogram, cervical dilatation is typically plotted against time (usually on the Y-axis) to show the progress of labor. This allows for a visual assessment of the rate of dilatation and any potential deviations from the expected pattern. By plotting cervical dilatation against time, healthcare providers can identify any potential issues with the progress of labor and make informed decisions regarding the need for interventions.

**Why Each Wrong Option is Incorrect**
**Option B:** Descent of head in Y-axis - This is incorrect because the descent of the head is typically plotted on the X-axis, not the Y-axis. The Y-axis usually represents the time or cervical dilatation.
**Option C:** Sigmoid shaped curve - This is incorrect because a normal partogram typically shows a gradual increase in cervical dilatation and fetal head descent, rather than a sigmoid-shaped curve. A sigmoid-shaped curve may indicate a prolonged or abnormal labor.
**Option D:** A line followed 4 hours later by action line - This is incorrect because the partogram typically includes a series of lines or curves that represent the progress of labor, rather than a single line followed by an action line. The action line represents the point at which intervention may be necessary if labor is not progressing normally.

**Clinical Pearl / High-Yield Fact**
A normal partogram should show a gradual increase in cervical dilatation and fetal head descent, with a slope of at least 1 cm/hour for cervical dilatation. Deviations from this pattern may indicate a potential complication and require further investigation.

**✓ Correct Answer: A. Cervical dilatation in X-axis**