A radiograph is shown below. This type of root morphology has highest incidence in which population?
African
Caucasians
Mongoloids
Asians
A variation in root morphology is the presence of an extra distolingual root. Usually, this root has a type 1 canal configuration. Two-thirds of the first mandibular molars found in a Chinese population had this variation. Similarly, this distolingual root occurred in 4% of mandibular first molars of a Kuwaiti population. These results confirm the observation that East Asian populations have more three-rooted mandibular first molars than do other racial groups. Mandibular molars, mainly first molars, may also have an additional root located lingually or buccally. Although this is a rare occurrence in Caucasian populations, it is more common in Asian populations. The radix entomolaris (RE) is a supernumerary root located distolingually in mandibular molars, whereas the radix paramolaris (RP) is an extra root located mesiobuccally. Each root usually contains a single root canal. The orifice of the RE is located distolingually to mesiolingually from the main canal or canals of the distal root; the orifice of the RP is located mesiobuccally to distobuccally from the main mesial root canals. 
Key Concept:
The figure in the question show radix entomolaris.