Réponse :
a. When we were in London, we visited the Science Museum.
b. We were very quiet, because the guide was talking.
c. We couldn't touch anything : security guards were watching us all the time.
d. I took a photo when the guards were not looking.
e. The museum was very big, so we had lunch in the cafeteria.
f. I was buying a postcard when my phone rang.
Explications :