题干
190. The famous scientist began the research which his new discoveries.
A：belonged to
B：led to
C：caused to
D：brought to
答案(点此获取答案解析）
B
A：belonged to
B：led to
C：caused to
D：brought to
的各棱长都为2，E，F分别是
的中点，则EF的长是 （ ）
