💡 Detailed Explanation
The phrase '様相を呈する (yōsō o tei suru)' is an idiom meaning 'to take on a certain state or appearance.' '様相 (yōsō)' means the state or appearance of things. In this sentence, it means the conflict has started to show signs of becoming prolonged. The other choices do not fit the context. '様式 (yōshiki)' means style or format, '形態 (keitai)' means form or shape, and '情勢 (jōsei)' refers to the state of affairs, but it is not used with the verb '呈する' in this manner.