The oxygenation activity of RuBisCo (Ribulose-1,5-bisphosphate carboxylase/oxygenase) in photorespiration leads to the formation of:

Option A

This implies the production of 1 molecule of a 3-carbon compound (3-phosphoglycerate) and 1 molecule of a 2-carbon compound (2-phosphoglycolate).

In detail, RuBisCo facilitates the reaction where ribulose-1,5-bisphosphate reacts with O$_2$ instead of CO$_2$. This process yields one 3-phosphoglycerate (3-PGA) and one 2-phosphoglycolate, which is a distinctive feature of the oxygenation process in photorespiration as opposed to the carboxylation process in the Calvin cycle which produces two molecules of 3-PGA.

Thus, in the context of photorespiration:

$$ \text{Ribulose-1,5-bisphosphate} + \text{O}_2 \rightarrow \text{3-phosphoglycerate} + \text{2-phosphoglycolate} $$

This results in 1 molecule of a 3-carbon compound and 1 molecule of a 2-carbon compound.