Question

They ... Computer when I arrived
1.were playing 2. Are playing 3.play 4. Was playing

Answer 1

They were playing computer when I arrived (1)

Answer 2

They were playing Computer when I arrived.

Когда мы говорим про продолжительное действие в прошлом которое было прервано коротким, мы используем конструкцию past continuous + past simple