The zygote undergoes repeated mitotic divisions which are known as cleavage. Cleavage takes place along definite planes to form a solid mass of cells. This solid ball-like structure is known as morula.

The answer to the question is option 'C': Morula.

Explanation:
The process of cleavage is the rapid division of cells in the early embryonic stage. It leads to the formation of a solid ball of cells known as a morula. Let's understand the concept and terminology associated with early embryonic development:

1. Cleavage:
Cleavage is the process of cell division that occurs after fertilization. It involves repeated mitotic divisions of the zygote (fertilized egg) without any significant growth. These divisions result in the formation of smaller cells called blastomeres.

2. Blastula:
Blastula is the next stage in embryonic development after the morula. It is a hollow ball of cells, also known as a blastocyst in mammals. The blastula consists of a single layer of cells called the blastoderm or blastodermic vesicle, surrounding a fluid-filled cavity called the blastocoel.

3. Gastrula:
Gastrulation is a crucial process in embryonic development that follows the blastula stage. It involves the rearrangement and migration of cells, leading to the formation of three primary germ layers: ectoderm, mesoderm, and endoderm. The embryo at this stage is called a gastrula.

4. Neurula:
Neurulation is a specific process that occurs during gastrulation in which the neural plate forms and eventually gives rise to the central nervous system. The embryo at this stage is called a neurula.

5. Morula:
Morula is the early stage of embryonic development that follows cleavage. It is a solid ball of cells consisting of blastomeres. The morula stage typically consists of 16-32 cells. The cells in the morula are tightly packed together and have not yet formed a blastocoel.

Conclusion:
In summary, a solid ball of cells produced by repeated cleavage is called a morula. It is an early stage of embryonic development before the formation of a blastula or gastrula. The morula stage precedes the blastula stage, which is characterized by the presence of a fluid-filled cavity called the blastocoel.