His parents always tells him_________ to bed early because it’s good for his health.

You are under 18 years old, so it is for you to join the Trailwalker.

The sentence structure（结构）of “He often makes me happy” is ________.

(2013·高考山东卷)There is no simple answer，________ is often the case in science.

Could you imagine a future changed by technology ________ our lessons are taught by robots rather than human teachers