Final answer:
The term 'circadian rhythm' refers to the 24-hour cycle in the physiological processes of living beings. Among the options provided, the pattern of rats showing daily activity even in constant light is the most accurate example of circadian rhythm.
Step-by-step explanation:
The strongest example of circadian rhythm among the given options is: d. Rats kept in constant light show a daily pattern of activity. Circadian rhythms are physical, mental, and behavioral changes that follow a roughly 24-hour cycle, responding mainly to light and darkness in an organism's environment. They are found in most living things, including animals, plants, and many tiny microbes. The study of circadian rhythms is called chronobiology.
The daily pattern of activity observed in rats, even when they are kept in constant light, is a direct manifestation of these built-in biological cycles. The other options provided do not represent circadian rhythms but rather other types of biological or behavioral phenomena: sensing tides, being more active in mild weather, and sensing changes in the Earth's magnetic field do not directly relate to the body's intrinsic daily cycle.