单选题 He frequently wandered from his text to ______ on a point that had obviously caught his audience's interest.

【正确答案】 A

【答案解析】(elaborate on/upon详述)。句意为：他经常偏离正题，详述某个显然能引起听众兴趣的论点。B．stress强调；C．interrupt打扰；D．illustrate阐明。