**Core Concept**
The progression of dental caries on pits and fissures involves the demineralization of enamel and dentin due to acid production from bacterial fermentation of carbohydrates. This process is influenced by the presence of Streptococcus mutans, a primary cariogenic bacterium.

**Why the Correct Answer is Right**
The correct answer is related to the enamel caries progression, which starts from the pit or fissure. The bacterial plaque accumulation and acid production lead to the demineralization of the enamel, creating an initial lesion. As the acid production continues, the enamel lesion progresses, and the dentin is affected, leading to dentin caries. This progression is influenced by the pH of the oral environment and the buffering capacity of saliva.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not specify the progression of dental caries on pits and fissures. While enamel caries can occur on any surface, the question specifically asks about pits and fissures.
**Option B:** This option is incorrect because it does not accurately describe the progression of dental caries on pits and fissures. The correct progression is from enamel to dentin, not from dentin to enamel.
**Option C:** This option is incorrect because it does not specify the progression of dental caries on pits and fissures. While dentin caries can occur on any surface, the question specifically asks about pits and fissures.

**Clinical Pearl / High-Yield Fact**
The most susceptible areas for dental caries are the occlusal surfaces of molars and premolars, particularly in the deep grooves and fissures. Regular dental cleanings and fluoride treatments can help prevent the progression of dental caries on these surfaces.

**Correct Answer:** A.