**Core Concept**
Prolonged labour is a condition where the duration of labour exceeds the normal expected time, leading to potential complications for both mother and fetus. The latent stage of labour is the initial phase, where the cervix dilates from 0 to 4 cm.

**Why the Correct Answer is Right**
The latent stage of labour typically lasts around 12 to 24 hours in primigravidas (first-time mothers) and 6 to 12 hours in multigravidas (multiparous women). The American College of Obstetricians and Gynecologists (ACOG) defines prolonged latent phase as a duration exceeding 20 hours in primigravidas and 14 hours in multigravidas.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as there is no standard definition for prolonged latent phase in primigravidas or multigravidas. Different institutions may have varying criteria.

**Option B:** This option is incorrect as the duration of 8 hours is too short for the latent stage of labour, even in multigravidas.

**Option C:** This option is incorrect as the duration of 24 hours is too long for the latent stage of labour, even in primigravidas.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the definition of prolonged latent phase may vary slightly between institutions, but 20 hours for primigravidas and 14 hours for multigravidas is a commonly accepted standard.

**Correct Answer:** C. 24 hours