严格按设计要求,()计算下井管柱的各段长度、根数和管柱总长度。
A、自下而上
B、自上而下
C、自中间而上
D、自中间而下
参考答案:B
Just a few minutes every day, _______ you could have shining floors and furniture with this new cleaner.
A.but
B.and
C.or
D.so
误机指旅客因证件不符合规定而未能乘机。