培训期间，威廉学习了高速螺旋桨飞机和直升机驾驶技术等课程。

William learnt how to fly fast propeller-powered planes and helicopters during the four-month RAF training.(See photo)

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课程的螺旋式设计确保持续复习以稳固提高自然发音技能。

The spiral design of the program ensures constant review and steady build-up of the phonics skills.

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Remember I talk those of you who were here the first time: this course is built like a spiral Everything is intra-connected, what I talked about in the first class is connected to what I'm going to talk about today, is going to be connected to lecture 19.

记得一开始我就跟你们说过：,这课程就像个螺旋,内部的一切都是相关的，第一节课讲到的内容,与今天要谈的课题有关，也和第19课有关。

哈佛公开课 - 幸福课课程节选