**Core Concept**
Tumor-containing cells of all three germ layers are called teratomas, which are a type of germ cell tumor. Teratomas are composed of cells from all three germ layers: ectoderm, mesoderm, and endoderm. This characteristic allows them to differentiate into various tissues and organs.

**Why the Correct Answer is Right**
Teratomas arise from primordial germ cells that are present in the early embryo. These cells have the ability to migrate to different parts of the body and differentiate into cells of all three germ layers. As a result, teratomas can contain a wide range of tissue types, including hair, muscle, bone, and teeth. The presence of cells from all three germ layers is a hallmark of teratomas and distinguishes them from other types of tumors.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not specified, but it is likely incorrect because it does not accurately describe the composition of teratomas.
**Option B:** This option may refer to a type of tumor that is specific to one germ layer, such as a neuroblastoma (ectoderm) or a rhabdomyosarcoma (mesoderm).
**Option C:** This option may refer to a type of tumor that is composed of cells from a single germ layer, such as a seminoma (germ cell tumor of the testis).

**Clinical Pearl / High-Yield Fact**
Teratomas are often associated with the presence of a Y chromosome in females, which can occur due to chromosomal mosaicism. This can lead to the development of a teratoma in a female patient.

**Correct Answer: C. Teratomas**