b$)$ The repetitive units that develop into teeth have been proposed to form through a reaction$-$diffusion mechanism. Given this mechanism, speculate how the domestication syndrome may contribute to the formation of a single central incisor.$$

i$)$ decrease in neural crest cell input results in decreased size of field where tooth primordia develop, leading to a reduced number of reaction$-$diffusion$-$generated units

ii$)$ decrease in neural crest cell input results in increased size of field where tooth primordia develop, leading to a reduced number of reaction$-$diffusion$-$generated units

iii$)$ reduced neural crest cell input leads to variations in reaction$-$diffusion parameters, resulting in a reduced number of reaction$-$diffusion$-$generated units

iv$)$ reduced neural crest cell input increases conservation in phylotypic period gene networks, resulting in changes in the number of reaction$-$diffusion$-$generated units

v$)($i$)$ and$/$or $($iii$)$