Which process involves adjusting the biological clock to match the external environment?

The process that involves adjusting the biological clock to align with the external environment is synchronization. This term refers specifically to the act of aligning internal biological rhythms, such as circadian rhythms, with external cues like light and dark cycles. Synchronization plays a crucial role in ensuring that an organism's physiological processes are in harmony with the time of day, allowing for optimal functioning throughout the day and night.

In this context, synchronization is vital because it helps maintain the regular cycle of sleep, feeding, hormone release, and other bodily functions that are influenced by the environment. When the environment changes, such as with shifting time zones or seasonal changes, synchronization ensures the biological clock adjusts accordingly to these external factors.

The other options, while related to biological and environmental interactions, do not specifically encapsulate this process of aligning the internal clock with external cues. Resynchronization might imply a focus on re-adjusting after a disruption but does not emphasize the initial alignment itself. Acclimatization refers more to physiological adjustments to environmental changes over time rather than the immediate synchronization of internal clocks. Regulation is a broader term that could apply to various forms of control over biological processes but lacks the specific connotation of aligning with environmental stimuli that synchronization has.