What acts as a bransted lowry acid but not as a bransted lowry base?

Acids which donote protons(releases H+, but not necessarily in water) are Bronsted-Lowry acids. Bases which accepts protons(H+) are called Bronsted-Lowry base (example : NH3). Hope this helps!

Most likely a is the answer - because  you generate   38 atp's but also consume an atp.   each atp gives approx. less than 4 kcal so probably a is the closest answer.