**Core Concept**
The primary immune response is a type of adaptive immune response that occurs upon the first encounter with an antigen. It is characterized by the activation of naive T and B cells, which then proliferate and differentiate into effector cells that recognize and eliminate the antigen.

**Why the Correct Answer is Right**
The primary immune response is indeed characterized by the activation of naive T and B cells, which then undergo clonal expansion and differentiation into effector cells. This process involves the recognition of the antigen by the T cell receptor (TCR) on T cells and the B cell receptor (BCR) on B cells, which triggers a signaling cascade that leads to the activation of these cells. The activated T cells then help to activate B cells, which differentiate into plasma cells that produce antibodies to neutralize the antigen.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify what is false about the primary immune response. Without more information, it is unclear what this option is trying to claim.
**Option B:** This option is incorrect because it is too vague and does not provide any specific information about the primary immune response.
**Option C:** This option is incorrect because it is not clear what it is trying to claim. Without more information, it is impossible to determine whether this option is correct or not.
**Option D:** This option is incorrect because it is not clear what it is trying to claim. Without more information, it is impossible to determine whether this option is correct or not.

**Clinical Pearl / High-Yield Fact**
It's worth noting that the primary immune response is often slow to develop and may not provide adequate protection against infection or disease. This is why vaccines often stimulate a secondary immune response, which is faster and more effective at providing protection.

**Correct Answer:** D