Step 1: Recall what revisit time is.
Revisit time is how long a satellite takes before it looks at the very same spot on Earth again.
Step 2: Connect swath to revisit time.
A sensor that sees a very wide strip of ground in one pass can cover the whole planet quickly, so it returns to the same place sooner.
Step 3: Look at MODIS.
MODIS rides on the Terra and Aqua satellites and has a very wide swath of about 2330 km.
Step 4: Work out the coverage.
With such a broad view, MODIS scans almost the entire Earth in just one to two days.
Step 5: Reject the longer times.
Values like 16 days or 6 days belong to narrow-swath, fine-resolution sensors, not to MODIS.
Step 6: Conclusion.
So the revisit time of MODIS is about 2 days.
\[ \boxed{2 \text{ days}} \]