Complete with: there or it.

I … there was a lot of information to remember. … was very difficult.

2 …it's impossible to know what changes will be to data storage in the future.

3 … there's nothing we can do but wait.

4 . it's time to upgrade our computer. . there are some fantastic laptops available now.

5 it's a pity I couldn't come but there was nothing I could do about it.