Your friends ask you how you manage to keep yourself so fit. You have the habit of going for daily walks in the morning. So you say:

The correct answer is D because present simple tense ('take') correctly describes a habitual or regular action (daily morning walks). Options A uses 'will take' (future tense) which suggests a one-time future action, not a habit. Option B uses 'used to take' (past habit) which implies the speaker no longer does this. Option C uses present continuous ('am taking') which describes an action happening right now, not a regular habit.