纳粹氧化镁是一种新型高功能精细无机材料，制备工艺流程如图，请回答下列问题：

观察下图，完成以下填空。

已知HCN的电离常数K＝6.2×10^-10.用物质的量都是0.1mol的HCN和NaCN混合后配成1L溶液，经测定溶液呈碱性．则下列关系式正确的是

如图所示，刻度尺的分度值是____，物体的长度是____．

根据短文内容，选择正确答案。
D
    John sent for a doctor because his wife was ill. He called the doctor and made sure they would meet at five. He arrived at the doctor's at twenty to five. He thought. “It s a little bit earlier. I'll wait for a moment. It's good to keep the time. ”
    Then he stopped his car in front of the doctor's. He looked around and saw a noisy square not far from here. He went there and sat down on a chair to enjoy the last light of afternoon sun and make himself quiet. He saw some children playing and some women talking to each other happily.
    Suddenly he heard a girl crying. He came up to her and asked some questions. Then he knew she got lost. John tried to find out her address and took her home. The girl's parents were very thankful.
    Then John hurried to the doctor's. The doctor said angrily when he saw him “You're late. Why did you keep me waiting for 20 minutes?" John said nothing but one word "Sorry!”