Morula is how many celled –

**Core Concept**
The morula is an early-stage embryo consisting of a compact cluster of cells. It is a critical stage in embryonic development, preceding the blastocyst stage. This stage is characterized by the **compaction** of the embryo.

**Why the Correct Answer is Right**
The morula stage typically occurs around 3-4 days post-fertilization and is composed of 16 cells, although this number can slightly vary. The **compaction process** involves the tightening of the cell connections, which helps in the formation of the outer trophoblast and inner cell mass. This process is crucial for the further development of the embryo.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it suggests a much earlier stage of development.
**Option B:** This is also incorrect as it represents a later stage in embryonic development.
**Option D:** Similarly, this option is incorrect as it does not accurately represent the number of cells in a morula.

**Clinical Pearl / High-Yield Fact**
The morula stage is a critical point in **in vitro fertilization (IVF)** protocols, where the embryo's development is closely monitored before transfer. Understanding the timing and cellular composition of the morula is essential for optimizing IVF outcomes.

**Correct Answer:** C. 16