Final answer:
Personal bias is especially difficult to overcome among the listed communication barriers as it is deeply rooted in an individual's beliefs and can significantly affect perception and interpretation.
Step-by-step explanation:
Among the communication barriers listed, personal bias is very difficult to overcome because it is deeply ingrained in individuals' belief systems and worldviews. Language differences, while challenging, can be bridged through translation and learning.
Semantic barriers can often be clarified with definitions and explanations. physical barriers can typically be addressed through technological solutions or environmental adjustments.
However, personal bias affects perception and interpretation in such a subjective manner that even with awareness, it can require significant effort and reflection to change. Overcoming personal bias requires open-mindedness and the willingness to challenge one's own assumptions, which can be difficult to achieve.