Which term refers to careful awareness of external factors?

The term that signifies careful awareness of external factors is "vigilant." Being vigilant implies a state of alertness and attentiveness to potential changes or dangers in one’s surroundings. This characteristic is particularly important in contexts where awareness can prevent harm or facilitate better decision-making.

In contrast, the other terms lack this connotation of active awareness. "Careless" suggests a lack of attention or concern, which directly opposes the essence of being vigilant. "Negligent" also indicates a failure to take proper care or to attend to important details. Similarly, "indifferent" describes a lack of interest or concern, suggesting a passive approach to awareness. Thus, among the options, "vigilant" is the most appropriate choice to convey the idea of careful awareness of external factors.