**Core Concept**
The six keys to normal occlusion is a concept in orthodontics that describes the fundamental principles of a well-aligned and functional dentition. It was introduced to guide orthodontic treatment and ensure proper occlusal relationships between the upper and lower teeth.

**Why the Correct Answer is Right**
The six keys to normal occlusion were first proposed by Dewey in 1904. They include:
* Key 1: The mesial surfaces of the maxillary first molars should occlude with the buccal surfaces of the mandibular first molars.
* Key 2: The mesial surfaces of the maxillary second molars should occlude with the buccal surfaces of the mandibular second molars.
* Key 3: The distal surfaces of the maxillary first molars should occlude with the buccal surfaces of the mandibular first premolars.
* Key 4: The buccal surfaces of the maxillary first premolars should occlude with the lingual surfaces of the mandibular first premolars.
* Key 5: The occlusal surfaces of the maxillary and mandibular first molars should be in contact, with the maxillary first molar occluding with the buccal groove of the mandibular first molar.
* Key 6: The occlusal surfaces of the maxillary and mandibular second molars should be in contact, with the maxillary second molar occluding with the buccal groove of the mandibular second molar.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the six keys to normal occlusion were not introduced by Andrews.
**Option B:** This option is incorrect because the six keys to normal occlusion were not introduced by Tweed.
**Option C:** This option is incorrect because the six keys to normal occlusion were not introduced by Ricketts.

**Clinical Pearl / High-Yield Fact**
The six keys to normal occlusion serve as a guide for orthodontic treatment and ensure proper occlusal relationships between the upper and lower teeth. They are essential for achieving a well-aligned and functional dentition.

**Correct Answer: C. Dewey**