**Core Concept**
Rheumatic fever is a complication of untreated or inadequately treated group A beta-hemolytic streptococcal (GABHS) throat infections, and the interval between the throat infection and the onset of rheumatic fever is crucial for diagnosis. This interval is based on the concept of post-streptococcal reactive arthritis, where the immune system's response to the streptococcal infection leads to joint inflammation.

**Why the Correct Answer is Right**
The probable interval between throat infection and the onset of rheumatic fever is typically 2-3 weeks. This is because the immune system takes time to mount an effective response against the streptococcal infection, leading to the production of antibodies against the streptococcal antigens. These antibodies can cross-react with the host's own tissues, leading to the development of rheumatic fever. The correct interval is based on the Jones criteria, which are used for the diagnosis of rheumatic fever.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is too short, as it does not allow sufficient time for the immune system to respond to the streptococcal infection.
**Option B:** This option is too long, as it exceeds the typical time frame for the development of rheumatic fever.
**Option C:** This option is incorrect, as it does not specify a clear time interval.

**Clinical Pearl / High-Yield Fact**
It's essential to note that the Jones criteria for the diagnosis of rheumatic fever include major and minor criteria, which include clinical manifestations such as joint pain and fever, as well as laboratory findings such as elevated erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP).

**Correct Answer:** C. 21-28 days.