机夹式数控车床刀具根据刀体（）的不同，又可分为不转位和可转位两种，常用的是可转位的机夹刀具。
A．宽度
B．结构
C．形状
D．厚度
参考答案：B
（）的课堂气氛是恬静与活跃、热烈与深沉、宽松与严谨的有机统一。
A.积极
B.消极
C.对抗
D.放任
Cars Y and Z travel side by side at the same rate of speed along parallel roads as shown above. When car Y reaches point P, it forks to the left at angle x, changes speed, and continues to stay even with car Z as shown by the dotted line. The speed of car Y beyond point P is what percent of the speed of car Z ？（）
(1)the speed of car Z is 50 miles per hour.
(2)x=45
A.条件（1）充分，但条件（2）不充分.
B.条件（2）充分，但条件（1）不充分.
C.条件（1）和（2）单独都不充分，但条件（1）和条件（2）联合起来充分.
D.条件（1）充分，条件（2）也充分.
E.条件（1）和条件（2）单独都不充分，条件（1）和条件（2）联合起来也不充分.
