The correct answer is: D. no article
The word “school” is a common noun, which means it refers to a general class of things. In this case, the speaker is referring to a specific school, but they are not specifying which school. Therefore, they do not need to use an article.
If the speaker were to specify which school they are talking about, they would need to use an article. For example, they could say “We study in the same school.” In this case, the article “the” is used to indicate that the speaker is referring to a specific school that is known to both the speaker and the listener.
The articles “a” and “an” are used to refer to general classes of things. They are used when the speaker is not specifying which thing they are talking about. For example, the speaker could say “We study in a school.” In this case, the article “a” is used to indicate that the speaker is referring to any school, not a specific school.
In conclusion, the correct answer to the question “We study in . . . . . . . . same school” is “D. no article.” This is because the speaker is referring to a specific school, but they are not specifying which school. Therefore, they do not need to use an article.