I wonder which choice works and which doesn't work in each example and why?
- Jim went to answer the phone. ............., Nancy started to prepare lunch.
- You go to do the shoping. ................., I'll clean the house.
I think, in example #1, choices "a" and "c" and for the example #2, the choice "b" work. This is because to me, "meanwhile" in this sense is interchangeable with "at the same time". In addition, "meanwhile" is used when we are talking about the past events, whereas "in the meantime" is future-oriented.