All ____ you have to do is to press the button.填 What 还是that

All ____ you have to do is to press the button.填 What 还是that all you have (to do) is to press the button.能不能详细解释下为什么填to d 例句：All you have to do is (to) press the button.若主语有个实意动词do用作 What time ____ you go to school in the morning?填is,are,do或do All___you have to do is open your eyes.横线上填what 还是 that?为什么 press the red button to be liked To be a doctor is I wanted to be中填all that还是all what, All that we have to do is to practise everyday.能否将that改为what All ___ I ever wanted to do was to travel 填what 还是that?为什么? all you have to do is cry I don't know __ to do next?It's easy.Press the red button in press the blue button and you can listen to the music.(用if改写