Which of the following most directly made possible the age of exploration a: hydropower b: caraval c: aqueduct d: wind turbine

B: caraval

your answer is not A, because it was generally not researched and used yet.
your answer is not D, because it was generally not made, and even if it was in it's infant age, it would not have affected the age of exploration.

C, aqueduct, COULD have, but note "exploration". Aqueducts are generally used to bring water from a source to destination, and usually didn't help with exploration.

B: Caraval, is your answer, for it is a small, extremely manuervable boat that was used by Europeans to explore the outside world. Attached is a picture of a Caravel.

Again, your answer is B.

hope this helps