1. Put new sentences into the mailbox like in the example.

2. Put new sentences into the mailbox as in the example.
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Which one do we have to use, 'like' or 'as'?

3. Put the proper be verb into each blank.

4. Put the proper be verb in each blank.

5. Put the proper verb be into each blank.

6. Put the proper verb be in each blank.
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Which one do we have to use between 'in' and 'into', and between ' the verb be' and 'the be verb'?

#2 better than #1.

#3 and #4 are both acceptable.
#5, we should say Put the proper form of the verb "to be" in each blank.
The same in #6.

1. Both "like" and "as" can be used in this context, but they have slightly different meanings. "Like" implies similarity or comparison between two things, while "as" implies that the action is being done in the same manner as the example. So, both sentences are grammatically correct, but the choice between "like" and "as" depends on the meaning you want to convey.

To determine which one to use, ask yourself if you want to emphasize similarity/comparison (use "like") or if you want to emphasize doing something in the same manner (use "as").

2. The same explanation applies here as in the previous question. Both sentences are grammatically correct, but the choice between "like" and "as" depends on the intended meaning.

3 and 4. Both options (using "in" or "into") are grammatically correct, but they convey slightly different meanings. "In" is used when the proper be verb already exists in the blank, and you are simply referring to it. "Into" is used when you are actively inserting or placing the proper be verb into the blank.

So, if you are referring to the blank that already has the proper be verb, use "in." If you are actively placing the proper be verb into the blank, use "into."

5 and 6. Both options (using "the verb be" or "the be verb") are grammatically correct, but "the verb be" is a more general and common way to refer to the be verb. However, "the be verb" can be used as well if you want to be more specific and explicit.

So, you can use either "the verb be" or "the be verb" based on your preference.