土方边坡自上而下分层开挖时，上台阶应比下台阶开挖深进不少于()
A.10m
B.20m
C.30m
D.40m
参考答案：C
He's been________as judge in the State Supreme Court in California. [ ]
A. determined
B. appointed
C. admitted
D. assumed
样本相关系数的假设检验，其备择假设为
A．ρ＝0B．r≠0C．ρ≠0D．两变量相关关系密切E．两变量有直线相关关系
