What has happened? vs. What happened?

1a . Dale is in the hospital . His car is broken . He ____________________ ____________________ a car ____________________ .
1b . Dale now is home and well . He ____________________ a car ____________________ three days ____________________ .
2a . Everyone is wet . Water is on the floor and they look sunburnt . They ____________________ ____________________ swimming .
2b . Now the floor is clean and everyone is dry . They ____________________ ____________________ .
3a . My dad is home . He is sleeping on the floor and I can smell wine from his breath . He ____________________ ____________________ a lot .
3b . My dad is sober now and he is working . But he ____________________ a lot ____________________ night .
4a . My brother is not working on his computer . It is not working . His computer ____________________ ____________________ down .
4b . My brother is working again . His computer ____________________ ____________________ , but he ____________________ ____________________ his computer .
5a . She looks sad and cannot get into her house . She ____________________ ____________________ her key .
5b . She now looks happy and can get into her house . She ____________________ her key , but she ____________________ ____________________ her key .
6a . My house is messy with a lot of ballons , cakes and pizzas , because we ____________________ ____________________ a party .
6b . The house is clean again because I ____________________ just ____________________ up everything . We ____________________ a ____________________ ____________________ weekend .