1. He got the boy to open the door.

2. The boy was gotten to open the door.
3. The boy was made to open the door.
4. The boy was asked to open the door.
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Which one is similar to #1? Are they all grammatical?

2 is incorrect.

All the others are fine.

All four sentences are grammatically correct, but they have slightly different meanings and implications. To determine which one is similar to sentence #1, let's analyze each sentence:

1. "He got the boy to open the door."
In this sentence, "he" is the subject who successfully convinced or persuaded the boy to open the door.

2. "The boy was gotten to open the door."
In this passive construction, the boy is the subject being influenced or persuaded by someone or something (not specified in this sentence) to open the door. "Gotten" is the past participle form of "get."

3. "The boy was made to open the door."
In this sentence, someone (not specified in this sentence) forced or compelled the boy to open the door.

4. "The boy was asked to open the door."
In this sentence, someone (not specified in this sentence) made a request or a simple inquiry to the boy, asking him to open the door.

Based on the meanings of the sentences, sentence #3, "The boy was made to open the door," is the most similar to sentence #1, "He got the boy to open the door." They both indicate that someone influenced or compelled the boy to open the door. However, #1 implies persuasion, while #3 implies a stronger level of force or coercion.