**Core Concept**
The axillary lymph nodes are a group of lymphoid tissues that play a crucial role in the drainage and filtration of lymph from the upper limb, breast, and chest wall. The axillary lymph nodes are divided into three levels based on their location and relationship to the pectoralis minor muscle.

**Why the Correct Answer is Right**
Level I axillary lymph nodes are located lateral to the pectoralis minor muscle and receive lymph from the breast, anterior chest wall, and upper limb. They are the most lateral group of axillary lymph nodes and are often the first site of metastasis for breast cancer. The lymphatic vessels from the breast and anterior chest wall drain into the level I axillary lymph nodes, which then drain into the level II and III axillary lymph nodes.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because level II axillary lymph nodes are located posterior to the pectoralis minor muscle and receive lymph from the level I axillary lymph nodes, as well as from the posterior chest wall and scapular region.
**Option B:** This option is incorrect because level III axillary lymph nodes are located medial to the pectoralis minor muscle and receive lymph from the level II axillary lymph nodes, as well as from the posterior chest wall and scapular region.
**Option C:** This option is incorrect because it is not a valid answer choice.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that the axillary lymph nodes are divided into three levels, and the level I axillary lymph nodes are the most lateral group, receiving lymph from the breast and anterior chest wall.

**Correct Answer: A. Level I axillary lymph nodes are present.**