Time expression with perfect aspect: choose the correct preposition for a finished duration up to now. Sentence: I haven't seen you ____ a week. Select the option that fits a period of time (duration).

Given data

• Sentence: I haven't seen you ____ a week.
• Present perfect negative expresses non-occurrence up to now.

Concept/Approach
For is used with durations (a week, two years). Since marks a starting point (since Monday). During applies within a named period (during the week), and from needs a complement (from … to …).

Option analysis
for — correct with durations: for a week. ✅since — would require a point in time (e.g., since last week). ❌during — mismatched with perfect aspect and unspecified period. ❌from — incomplete without to/till. ❌

Final Answer
for