The correct option is B Enzyme
Suspension of isolated thylakoids in culture medium containing CO2 and H2O does not produce hexose (glucose), because of the absence of enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase. To produce hexose sugar RuBisco enzyme is necessary which catalyses the reaction. Isolated thylakoids can alsorb sunlight and produce ATP and NADPH, but to produce sugar (carbohydrates) enzyme RuBisco is necessary. So option "b" is correct.