A reaction step with ΔG∘=+55.0kJmol−1 must be driven by coupling to one or more of the reactions in the list below. Each driving reaction may be used at most once. Which option provides an overall spontaneous process with the **smallest magnitude of negative overall ΔG∘**?
Available driving reactions:
1. Hydrolysis of ATP → ADP + Pi ; ΔG∘=−30.5kJmol−1
2. Hydrolysis of PPi → 2 Pi ; ΔG∘=−19.2kJmol−1
3. Hydrolysis of creatine phosphate → creatine + Pi ; ΔG∘=−43.0kJmol−1
4. Hydrolysis of phosphoenolpyruvate → pyruvate + Pi ; ΔG∘=−61.9kJmol−1
a) Reactions 2 and 3
b) Only reaction 4
c) Reactions 1 and 2
d) Only reaction 1