What Product of the Light-Dependent Reactions is Released Directly into the Environment

Question

What product of the light-dependent reactions is released directly into the environment?  
A) O2
B) CO2
C) NADPH
D) ATP
E) Hydrogen ions

Accepted Answer

Oxygen (O2) is produced as a byproduct of photosynthesis during the light-dependent reactions and is released directly into the environment as oxygen gas.