$1.$Many people go to the city to look for a job.
$-> $Why do many people go to the city?
$2.$ It is about 100km from Ho Chi Minh City to Vung Tau.
$->$How far is it from HCMC to Vung Tau?
$3.$They go to the countryside once a month.
$->$How often do they go to the countryside?
$4.$After 5 hours travelling by car, they reached Dalat City.
$->$ When did they reach Dalat City?
$5.$They usually went to the park in the afternoon.
$->$When did they usually go to the park?
$6.$We had our picnic on the riverbank.
$->$Where did you have your picnic?
$7.$They had a picnic on the riverbank before going back home.
$->$What did they have before going back home?