Which of the following is an example of external depreciation?

External depreciation refers to a decrease in property value due to external factors that are outside the control of the property owner. The presence of a busy road nearby exemplifies external depreciation, as it can negatively impact the desirability of the property. Factors such as noise, traffic, and pollution from the road can detract potential buyers or tenants, thus reducing the property's overall value.

In contrast, the other options primarily relate to internal factors or owner-specific conditions that affect the property's value. Outdated features in a house and regular maintenance issues are directly tied to the condition and appeal of the property itself. A cluttered yard may suggest neglect or lack of upkeep, but it is more of a result of the owner's choices rather than an external influence. Therefore, external depreciation is accurately represented by the influence of a busy road, making it the correct choice.