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如图是某同学鉴别NH₄HCO₃、NH₄Cl、KCl三种化肥的过程，其中试剂甲和乙分别可能是（　　）

A．甲：熟石灰；    乙：稀盐酸

B．甲：水；    乙：氢氧化钠溶液

C．甲：氢氧化钠溶液；乙：稀硫酸

D．甲：稀盐酸；乙：氯化钠溶液

The origin of ____ life on earth is ____ question that interests astronomers.[ ]

A. the; the

B. \; a

C. \ ; the

D. the; a

—Jim, remember to return this book by Friday.

—_______.

A．Got it

B．Good luck

C．That's right

D．It's nothing

Once a decision has been made,all of us should  ____ it.       [ ]

A. direct to      

B. stick to        

C. lead to          

D. refer to

在一个L₈(2⁷)正交试验中，因子A、B、C、D的F比如表2.3-7所示，则辨别因子的显著性情况为（）。

表2.3-7

A．A因子(在6=0.05)为显著

B．B因子(在α=0.01)为显著

C．B因子(在α=0.05)为显著

D．C因子(在α=0.01)为显著

E．D因子为不显著