Hi Rose! It depends on the intention of the writer. 1. I'm (I am) going to open the book. "Going to", followed by the infinitive verb "open", refers to an action that will take place in the near future. 2. I have been opening the book. "Have been + verb+ing." "Have been opening" is present perfect continuous. It means that the action has taken place already and it is still continuing in the present. 3. I were opening the book. This construction of this sentence is grammatically incorrect. 4. I will be opening the book. "Will be + verb+ing." "Will be opening" is future continuous. It refers to an action that will occur at a particular time in the near future.

1

The first one is correct.

All apart from no.3 make sense

I'm opening the book