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【单选题】
有甲，乙，丙三个相互咬合的齿轮，当甲齿轮转了4圈时，乙齿轮转了9圈，丙齿轮转了5圈，甲，乙，丙三个齿轮的齿数比是（ ）。
A.
B.
C.
D.
参考答案：
参考解析：
刷刷题刷刷变学霸
举一反三
【单选题】Passage 3 Questions 11 to 15 are based on the following passage: Scientists in India have invented a new way to produce electricity. Their invention does not get its power from oil, coal or other fuel...
A.
Because bullocks have long been used by Indian people
B.
Because bullocks walk slowly and are easy to control.
C.
Because there are few non-working bullocks in India
D.
Because there is not enough oil in India.
【多选题】下列是造成人工牙咬合过低的原因有()
A.
人工牙材质有缺陷，不耐磨
B.
缺牙区牙槽嵴吸收，基托下沉
C.
患者紧咬合，人工牙严重磨耗
D.
义齿装盒充胶时，充胶量不足
E.
义齿蜡型制作过程中，人工牙蜡型无咬合接触或接触不紧