To solve this problem, we need to determine the number of ATP and NADPH molecules required for the fixation of one molecule of CO$_2$ in the Calvin cycle.$\newline$The Calvin cycle, also known as the C$_3$ cycle, is the set of chemical reactions that take place in chloroplasts during photosynthesis.$\newline$Let's break down the process:$\newline \bullet$The Calvin cycle consists of three main phases: carbon fixation, reduction, and regeneration of RuBP (ribulose bisphosphate).$\newline \bullet$During the carbon fixation phase, CO$_2$ is fixed into an organic molecule.$\newline \bullet$In the reduction phase, ATP and NADPH are used to convert 3-phosphoglycerate into glyceraldehyde-3-phosphate (G3P).$\newline \bullet$For each CO$_2$ molecule fixed, the cycle requires 2 molecules of NADPH and 3 molecules of ATP.$\newline$Therefore, the correct answer is:$\newline$Option 4: 3 molecules of ATP and 2 molecules of NADPH.