提到宾语从句的三要素。那就要从宾语从句的定义开始理解。在句子中起名词作用的句子叫名词从句 (Noun Clauses)。名词从句的功能相当于名词词组, 它在复合句中能担任主语、宾语、表语、同位语、介词宾语等，从句在句子中充当什么成分，就叫什么从句，如：主语从句、宾语从句、表语从句和同位语从句。宾语从句是名词性从句的一部分。简单来说，在句子中起宾语作用的句子叫宾语从句，宾语从句在复合句中作主句的宾语。主句 +连词(引导词)+ 宾语从句
1. 当主从句的主语一致时：
1) I don’t know what I shall do next.
I don’t know what to do next.
2)John didn’t decide which shirt he would buy.
John didn’t decide which shirt to buy.
连词+宾语从句 → 连词+to do
I don’t know what I shall do next .
I don’t know what to do next .
She didn’t decide which one she would choose .
She didn’t decide which one to choose .
Please tell me whom you’ll give the letter to .
Please tell me whom to give the letter to
2. 当主句的谓语动词是order, require等时，如果主句和从句的主语 不一致，宾语从句可转化为“名词(代词)+不定式”
The headmaster ordered that we should start at once.
The headmaster ordered us to start at once.
The boss required that she (should) keep it a secret .
The boss required her to keep it a secret .
1. 当主从句的主语一致时：
1) I don’t know what I shall do next.
I don’t know what to do next.
2)John didn’t decide which shirt he would buy.
John didn’t decide which shirt to buy.
连词+宾语从句 → 连词+to do
I don’t know what I shall do next .
I don’t know what to do next .
She didn’t decide which one she would choose .
She didn’t decide which one to choose .
Please tell me whom you’ll give the letter to .
Please tell me whom to give the letter to
2. 当主句的谓语动词是order, require等时，如果主句和从句的主语 不一致，宾语从句可转化为“名词(代词)+不定式”
The headmaster ordered that we should start at once.
The headmaster ordered us to start at once.
The boss required that she (should) keep it a secret .
The boss required her to keep it a secret .
