The correct answer is: 10% of wall weight.
The weight of a foundation is assumed to be 10% of the weight of the wall. This is because the foundation needs to be strong enough to support the weight of the wall and any other loads that may be applied to it, such as the weight of a roof or other structures.
The other options are incorrect because they do not take into account the weight of the wall and other loads that may be applied to the foundation.
Option A: 5% of wall weight. This is too low of a percentage and would not be enough to support the weight of the wall and other loads.
Option B: 7% of wall weight. This is a bit higher than Option A, but it is still not enough to support the weight of the wall and other loads.
Option C: 10% of wall weight. This is the correct percentage because it takes into account the weight of the wall and other loads that may be applied to the foundation.
Option D: 12% of wall weight. This is too high of a percentage and would be more expensive than necessary.