Whenaspacecrafttravels,oneofthemajorproblemsisreentryintotheEarth’s_______.
A、surfaceHe_______tostudyharderinthefuturesothathecouldhavemoreopportunitiestofindabetterjob.
Thisriverformsanatural_______betweenChinaandKorea.
Weare_______attherapidprogressMarkhasmadeinthissemester.
Theengineersinthislabspentseveralweeks_______theirplansforthenewbicycle.
Afterworkingfortwentyhourswithoutanyrest,thedoctorswere_______.
