People around the country were excited the astronauts came back to the earth safely.
A. unless
B. but
C. until
D. because
网友回答
A. unless
B. but
C. until
(答案→)D. because
解析：考查连词。A. unless除非； B. but但是；C. until直到；D. because因为。句意：全国各地的人们都很激动，因为宇航员安全地返回地球。故D正确。