Here's why:
* Emphasis: The sentence is conveying the idea that the film was already in progress when the person arrived. The word "started" highlights this point.
* Natural Sentence Flow: In English, we tend to emphasize the last word in a sentence to create a natural rhythm.
Pronunciation:
* "Start" should be pronounced with a short "a" sound, similar to the "a" in "cat".
* "ed" should be pronounced as a separate syllable, with a short "e" sound.
Therefore, the stressed pronunciation of "started" would be: "start-ed".