1.1 I am writing an English exercise now. I was writing the exercise at that time yesterday.
Пояснение: Present Continuous используется для описания действия, происходящего сейчас, в момент речи (am writing). Past Continuous используется для описания действия, происходившего в определенный момент в прошлом (was writing at that time yesterday).
Ответ: I am writing an English exercise now. I was writing the exercise at that time yesterday.