[ Grammar ]
It is always interesting ——- people in airports while you’re waiting for a flight
A. being observed
B. observe
C. to have observed
D. to observe

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Vocabulary › Viewstretched or pulled tight; not loose or slack
A. artillery
B. taut
C. plunge
D. fray
Grammar › View
The cleaner ………… the floor every week.
A. sweeps
B. is sweeping
C. sweep