________和________在当今世界被人们视为社会发展的两大支柱。
参考答案：科技、教育
We began to open to the outside world in the late 1970s. ,there have been great changes in the country.
A．As a result of
B．As a result
C．First of all
D．After all
造渣剂形成焊接熔渣，可以保护（），使焊缝成形好。
A.熔滴
B.熔池
C.焊缝金属
