To solve this problem, we need to understand the oxygenation activity of the RuBisCo enzyme in photorespiration.$\newline \bullet$RuBisCo is an enzyme that catalyzes two different reactions: carboxylation and oxygenation.$\newline \bullet$In the oxygenation reaction, RuBisCo adds oxygen to ribulose-1,5-bisphosphate (RuBP) instead of carbon dioxide.$\newline \bullet$This reaction results in the formation of one molecule of 3-phosphoglycerate (a 3-carbon compound) and one molecule of phosphoglycolate (a 2-carbon compound).$\newline$Therefore, the oxygenation activity of RuBisCo in photorespiration leads to the formation of:$\newline \bullet$1 molecule of a 3-C compound (3-phosphoglycerate) and 1 molecule of a 2-C compound (phosphoglycolate).$\newline$This corresponds to Option 1: 1 molecule of 3-C compound.