题目

请阅读下面短文，根据短文内容,从方框内所给的选项中选出能填入空白处的最佳 选项，使短文意思通顺，并在答题卡上将该选项涂黑。选项中有一项为多余项。 Our smartphones are amazing, but our connections can be so slow. The future in sci-fi movies seems close, yet so far away. 5G technology makes that future look easily available. Schools, hospitals, transportation, factories — even our homes will soon use this powerful network.  54 Last year, China started testing 5G mobile networks in several cities across network.  55  To t设A，B，C是圆x2＋y2＝1上不同的三个点，且·＝0，存在实数λ，μ，使得＝λ＋μ，实数λ，μ的关系为(  )A．λ2＋μ2＝1B．＋＝1C．λ·μ＝1D．λ＋μ＝1