核心问题
（1）I'm glad that you are keeping up your studies. 我很高兴你在坚持学习。
(2)... but my hostess insisted on sending for a doctor. ……但是女主人坚持要请医生来。
keep up 与 insist on 都译作“坚持”，它们有无区别呢？
词典解答
keep up(up 为副词)是指“继续”意义上的“坚持”（即“不松懈”），而 insist on(on 为介词)是指“坚决要求”“坚持要干某事”的“坚持”（参见 insist on/keep up）。例如：
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Jane will have to keep up her piano practice if she wants to be a professional concert performer. 如果简想成为一个职业音乐会演奏家，就得坚持练习钢琴。
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You boys have done some very good work; I hope you can keep it up. 你们小伙子们干了一些很漂亮的工作。我希望你们能坚持下去。
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I insisted on driving him home. 我坚持要开车送他回家。
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Many workers now insist on a smoke-free environment. 现在许多工人都坚持要求有一个无烟的环境。