Answer:
The correct answer is:
Can you please send me the confidential folder? (a.)
Explanation:
The statement is a question, which needs to be answered, and in order to write a question, the writer add the punctuation mark "?", at the end of the sentence to denote that what is being said is a question, and if it is wrtten exactly in the speaker's words (verbatim), not in reported speech.
The sentence started with "Can you", and that automatically changes the whole sentence into a question, no matter the arrangement of words that follow. If the speaker had said, " Please send me the confidential folder", there would be no need for a question mark (?), because it is not a question, also if the statement was written in reported speech like " He asked if I could send him the confidential folder", then there would be no need for a question mark
other words used to start a question are, why, how, who, when, where, etc. and when used to start a sentence in the the speakers words verbatim, it is accompanied by a question mark.
