The police are now monitoring criminal/gang/drug 'activity' in the area.
There has been an increase in the city's (level of) economic 'activity'.
The instruments are used to detect volcanic 'activity' on the island.
(..) is most impressed with you. I think he overestimates my abilities, sir. Do you? Definitely. What about your activities outside the classroom? Sir? Well, I notice you've spent a great deal of time with Miss Granger. I can't help wondering if-- (..)2009 Harry Potter and the Half-Blood Prince