Final answer:
The practice of taking personal journeys is an ancient human activity, likely as old as civilization itself, which dates back to roughly 10,000 years. The best answer is 'Incomputable time' since journeys have been a constant aspect of human life since the emergence of complex societies. Option D is correct.
Step-by-step explanation:
People have been undertaking personal journeys since the dawn of civilization. Considering that human civilization is roughly 10,000 years old, personal journeys would similarly span a vast timeline. Ancient Egyptian civilization itself lasted for more than 3000 years, and this is just one example of the historical depth we are looking at. References to travels and explorations are found as early as in Mesopotamia and Egypt, where they created calendars initially based on the reigns of kings or the seasons dictated by their gods. Furthermore, the lifetime of a communicating civilization has been mentioned to be measured in years, and our ability to communicate across vast distances has been a recent development when viewed against the backdrop of human history.
Given the historical context and the continuities seen in civilizations such as Ancient Egypt, the option that best fits the timeline of personal journeys would be 'Incomputable time', as humans have been embarking on personal journeys for as long as we have had the means and motivations to do so, making the practice incredibly ancient and indeed difficult to quantify.