The correct option to fill in the blanks in the sentence “Excuse me, do you mind … I smoke?” is B. if. So, the completed sentence is: “Excuse me, do you mind if I smoke?”

Here’s why:

• A. because: This option is incorrect because “because” is used to show a cause or reason. In this context, we are asking for permission, not providing a reason.

• B. if: This is the correct option. “If” is used to ask a question or talk about a possible situation, which fits in this context where we are asking for permission.

• C. since: This option is incorrect because “since” is used to refer to a time or a reason. In this context, we are asking for permission, not referring to a time or reason.

• D. while: This option is incorrect because “while” is used to talk about something that happens at the same time as something else. In this context, we are asking for permission, not talking about simultaneous actions.

• E. against: This option is incorrect because “against” usually indicates opposition or resistance, which doesn’t make sense in this context.