**Core Concept**
The process of fertilization involves the fusion of a sperm with an egg (ovum) outside the body, typically in the ampulla of the fallopian tube. The resulting zygote undergoes cleavage, forming a blastocyst that travels through the fallopian tube towards the uterus. The zona pellucida, a glycoprotein layer surrounding the zygote, plays a crucial role in fertilization and early embryonic development.

**Why the Correct Answer is Right**
The zygote, with its zona pellucida, reaches the uterine cavity due to the movement of the fallopian tube's muscular layer, known as the musculature of the isthmus and ampulla. The muscular contractions propel the zygote through the fallopian tube towards the uterus. This process is essential for the implantation of the blastocyst in the uterine endometrium. The zona pellucida helps guide the zygote through the fallopian tube by interacting with the cilia and the muscular contractions of the tube.

**Why Each Wrong Option is Incorrect**
**Option A:** This option does not specify the correct pathway for the zygote to reach the uterine cavity. The zygote does not reach the uterine cavity through the cervix or vagina.
**Option B:** This option is incorrect as the zygote does not travel through the abdominal cavity to reach the uterine cavity.
**Option C:** This option is not a valid pathway for the zygote to reach the uterine cavity.

**Clinical Pearl / High-Yield Fact**
A key aspect of embryonic development is the implantation of the blastocyst in the uterine endometrium, which typically occurs 6-10 days after fertilization. The zona pellucida plays a crucial role in guiding the zygote through the fallopian tube and facilitating implantation.

**Correct Answer: C. Through the fallopian tube.**