The number of amphoteric, basic, and acidic oxides among the following respectively are:
\[
\text{CrO}_3, \, \text{MgO}, \, \text{K}_2\text{O}, \, \text{B}_2\text{O}_3, \, \text{Al}_2\text{O}_3, \, \text{In}_2\text{O}_3, \, \text{PbO}, \, \text{As}_2\text{O}_3
\]