A baby boy aged two years is admitted to play school and passes through a dental check-up. The dentist observed that the boy had twenty teeth. Which teeth were absent?

[Image comparing deciduous and permanent human dentition] A $2$ -year-old child has deciduous (milk) teeth. The dental formula for milk teeth is $\frac{2102}{2102}$. This means they have incisors, canines, and molars, but pre-molars are absent.