Help Detective Miller complete her observation report by choosing the correct verb form for each blank.

Detective Miller watched the suspect sipping his coffee nervously for several minutes. Suddenly, she saw him drop a small envelope onto the floor and quickly walk away.

Detective Miller watched the suspect sipping his coffee nervously for several minutes.

After verbs of perception like watch, see, or hear, we use the -ing form (present participle) to describe an action that is ongoing or in progress. The detective watched him over a period of time.

Suddenly, she saw him drop a small envelope onto the floor and quickly walk away.

We use the bare infinitive (the base verb without "to") after verbs of perception to describe a complete, finished action from start to finish. Dropping the envelope was a quick, completed event.