Under which condition can wildlife be legally killed, according to principles of wildlife conservation?

The principle behind the correct answer emphasizes that wildlife can be legally killed only for a legitimate purpose. This reflects the fundamental tenets of wildlife conservation, which prioritize the management of wildlife populations and the welfare of species over personal interests or recreation.

A legitimate purpose could include instances such as preventing damage to crops, maintaining ecological balance, or protecting public safety. For instance, if a certain species is overpopulated or invasive, wildlife management authorities may allow for culling to preserve the ecosystem's integrity. This ties back to the essence of conservation, where human actions towards wildlife are guided by objectives that support ecological health rather than selfish motives or mere recreation.

The other options do not align with conservation principles, as they imply actions that are either self-serving, lack justification under wildlife management practices, or suggest that killing wildlife is permissible outside of well-regulated and justified scenarios.