Tom knew nothing about it his sister told him. [ ]
A. since
B. if
C. until
D. unless
答案:C
“人无我有,人有我优”指的是旅游资源开发条件中旅游资源的
A.市场距离
B.游览价值
C.地区接待能力
D.交通位置及其通达性
设定关节坐标系时,机器人的S、L、U、R、B、T各轴()运动。