题干

已知a、b∈{2,3,4,5,6,7,8,9},则logab的不同取值个数为(   )

A:53

B:56

C:55

D:57

上一题 下一题 0.0难度 选择题 更新时间:2018-02-20 11:11:53

答案(点此获取答案解析)

A

同类题4

阅读下面短文,从每题所给的A、B、C和D四个选项中,选出最佳选项。

B

    Two weeks before my 12th birthday, my teacher asked me to conduct an experiment. When I mixed some powder together, they exploded. Molten liquid hit me in the face, but I felt no pain.

    I vividly remember standing there in a state of calm. I thought I was in a dream, but however hard I struggled to swim to the surface of consciousness, I couldn't wake up. I didn't understand how terrifying it was until I heard people saying, "Who's that?" That's when I knew I was unrecognizable.

    I was taken to hospital, but the doctors didn't know what to do with me. Later I was flown to Houston for surgery. Between the ages of 13 and 16, I had 40 operations. As each operation came and went, my vision would come back, then fade again. Eventually, it faded completely and I had what was left of my eyes removed for cosmetic reasons.

    Since then, I have lived in total darkness. Most blind people, even if they don't have any sight they're aware of, are still able to sense light. That gives them a sense of day and night. But not me. I absolutely lost that sense of time passing.

    For many years, I felt my sight loss darkening my life like the loss of my parents from which I would never recover. But when I was in my 40s, I realized I had to find a way to live. I trained to become a counselor, and that has helped me see my experiences in a different way. I can't fix people's broken lives — just like I can't fix my sight — but I can help them find a way to manage.

    Sometimes it feels as if all the struggles and negative experiences I've lived through were in fact a kind of preparation for helping others to make their own way towards the light.