Final answer:
Brennan's climb to ground level is represented by a positive integer since the climb is towards the wall, which has been defined as the positive direction. This is opposite to the direction of his starting position at the bottom of the wall, which would likely be represented by a negative integer.
Step-by-step explanation:
The question about Brennan climbing from the bottom of the wall to the ground level involves understanding integers and their direction about a reference point. Since the positive direction has been defined as towards the wall, the negative direction would be away from the wall. When Brennan climbs to the ground level, the integer representing this distance should be positive, as it is in the direction towards the wall, assuming the wall is at the ground level. If the bottom of the wall is considered to be at a negative initial position, the act of climbing up to ground level means moving in the opposite direction to the negative start point.
Therefore, the correct answer is: Positive; Opposite direction. This relates to the integer that represents the bottom of the wall because Brennan's initial position at the bottom would likely be a negative integer if below ground level, and the climb to ground level represents moving in the opposite direction from this negative starting position towards a positive final position.