如图，半圆形光滑轨道固定在水平地面上，半圆的直径与地面垂直，一小物块以速度v从轨道下端滑入轨道，并从轨道上端水平飞出，小物块落地点到轨道下端的距离与轨道半径有关，此距离最大时对应的轨道半径为（重力加速度为g）（　　）

△ABC中，tanA，tanB是方程6x²﹣5x+1=0的两根，则tanC=（　　）

根据《南京条约》文本，五口通商后，中方认为英人可在各口岸的港区居停，不得入城；英方则坚持要到城内活动。咸丰帝认为夷人入城事关中外大防，有损天朝体面。广州官府默许士绅煽动排外情绪，引发1849年反入城风潮。这反映出（  ）

    Mr Green is an Englishman. He teaches English well His English classes are very interesting. He likes us and we like him, too.
    Mr Green has two children----Mike and Nancy. Mike is eight and his sister Nancy is five. Mike goes to school but Nancy doesn’t. Mr Green likes to wear a T-shirt and a pair of jeans. Football is his favorite sport. After school we often have a basketball match. Sometimes Mr Green watches and joins us. He plays basketball just for us.

下面图形的周长是多少厘米？（   ）