Simple Past or Past Continuous?

Gapfill exercise

Enter your answers in the gaps. When you have entered all the answers, click on the "Check" button.
I (walk) in the park when suddenly a big dog (appear).
While Sue (watch) TV, Sally (sleep).
What (you, do) at 5 o’ clock yesterday?
Not much, I (relax) a lot.
When I (be) in Paris, an important letter (arrive).
When I (get) home, a man (climb) into my house through the window.
When I (meet) Liz she (cry).
I (leave) the house when the phone (ring).