孩子写作文，"我明天要去北京"写成 I will go 还是 I am going to go？好多人纠结到现在。
其实两者都对，差别在"是不是早想好了"。
will：临时一拍脑袋
电话响了，你说：I will answer it. 我去接。
下班路上突然想吃饭：I will have noodles tonight.
这种"当场决定、之前没计划"的，用 will。还有承诺、预测：
- I will help you. 我帮你。
- It will rain tomorrow. 明天会下雨。
be going to：早就计划好
你已经买了机票：I am going to visit my grandma this weekend.
天上乌云密布：Look at the clouds! It is going to rain.
这种"早有打算"或者"眼看就要发生"的，用 be going to。
句型变形
will 后面永远加动词原形，疑问把 will 提前：
- Will you come? / I won't be late.
be going to 里的 be 跟着主语变：
- I am going to / He is going to / They are going to.
一句口诀：临时决定 will 上，早有计划 be going to 站好岗。
