**Core Concept**
Optochin sensitivity is a key characteristic of *Streptococcus pneumoniae*, which is a type of Gram-positive diplococcus responsible for causing pneumonia, meningitis, and other invasive infections. Optochin is an antibiotic that selectively kills *S. pneumoniae* by inhibiting the enzyme DNA-dependent RNA polymerase.

**Why the Correct Answer is Right**
The correct answer is related to the use of optochin in the laboratory identification of *S. pneumoniae*. When a colony of *S. pneumoniae* is exposed to optochin, it will exhibit a zone of inhibition due to the antibiotic's bacteriostatic effects. This characteristic is used as a diagnostic tool to differentiate *S. pneumoniae* from other Streptococcus species. The mechanism of action of optochin involves the inhibition of DNA-dependent RNA polymerase, which is essential for bacterial transcription and replication.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not describe a characteristic of *S. pneumoniae* related to optochin sensitivity.
**Option B:** This option is incorrect as it does not accurately describe the mechanism of action of optochin.
**Option C:** This option is incorrect as it is not a recognized characteristic of *S. pneumoniae*.

**Clinical Pearl / High-Yield Fact**
When identifying *S. pneumoniae*, remember that optochin sensitivity is a key diagnostic feature. This can be tested using optochin disks on a culture plate, where *S. pneumoniae* will exhibit a zone of inhibition around the disk.

**Correct Answer: Not Provided**