国内外电信业务: overseas and domestic telecommunication services
了解: 1.(知道得清楚) understand; comprehend; acquaintance 短语和例子了解事物发展的规律 understand the laws of development of things; 一位优秀的教师必须了解儿童。 a good teacher must understand children. 你如果能正确和有效地使用一个字, 你就了解它了。