When carbon dioxide (CO₂) is dissolved in water, it undergoes a series of chemical reactions that result in various species being present in the solution. The reactions can be described as follows:

1. Carbon dioxide reacts with water to form carbonic acid:

$$CO_2 + H_2O \rightleftharpoons H_2CO_3$$

2. Carbonic acid can dissociate into a bicarbonate ion and a proton:

$$H_2CO_3 \rightleftharpoons HCO_3^- + H^+$$

3. Bicarbonate ion can further dissociate into a carbonate ion and a proton:

$$HCO_3^- \rightleftharpoons CO_3^{2-} + H^+$$

Based on these reactions, the species present in the solution when CO₂ is dissolved in water include CO₂, $$H_2CO_3$$, $$HCO_3^-$$, and $$CO_3^{2-}$$. Thus, the correct option is:

Option A: CO₂, H₂CO₃, $$HCO_3^-$$, $$CO_3^{2-}$$