**Core Concept**
The embryonic period, also known as the organogenesis stage, is a critical phase in fetal development that spans from the third week to the eighth week of gestation. During this period, the major organs and body systems begin to form and develop.

**Why the Correct Answer is Right**
The embryonic period is characterized by rapid cell division, growth, and differentiation, resulting in the formation of the three primary germ layers: ectoderm, mesoderm, and endoderm. These layers eventually give rise to all the tissues and organs in the body. The process of gastrulation, which occurs during the fourth week, marks the beginning of the formation of these germ layers. The embryonic period is a crucial time for the development of the central nervous system, cardiovascular system, and other vital organs.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately reflect the duration of the embryonic period.
**Option B:** This option is incorrect because it does not specify the correct duration of the embryonic period in weeks.
**Option C:** This option is incorrect because it is not a commonly accepted duration for the embryonic period.

**Clinical Pearl / High-Yield Fact**
A key fact to remember is that the embryonic period is a critical time for organogenesis, and any disruptions during this period can lead to congenital anomalies and birth defects.

**Correct Answer: D. The embryonic period spans from week 3 to week 8 of gestation.**