The enzyme that is not found in a C3 plant is

1.  RuBP carboxylase

2.  PEP carboxylase

3.  NADP reductase

4.  ATP synthase

PEP carboxylase enzyme is found in C4 plants to carry out the initial fixation of CO2.
 
The functions of other enzymes in options (a), (c), and (d) are as follows
(a) RuBP carboxylase operates in C3 plants.
(c) NADP reductase is involved in the electron transport chain.
(d) ATP synthase is used in ATP synthesis.