Final answer:
The acceleration of an object in free fall is constant at 9.8 m/s² due to gravity, regardless of the duration of the fall.
Step-by-step explanation:
The acceleration of an object in free fall, such as one dropped from the Transco Tower in Houston, is consistent: it is caused by gravity and equals 9.8 m/s². This acceleration is the same no matter how long the object has been falling - at the second second, the fifteenth second, and so on. Hence, the correct answer is a) 9.8 m/s².