按照救生艇安全操作规定,除救生演习外,操艇人员由船长决定,非机动艇不少于()人,机动艇不少于()人。
A.9/7
B.7/5
C.7/9
D.4/7
参考答案:B
—____ _?
—We are from Guangdong.
A.Who are you B. Where are you from C. How are you
渐开线齿轮的正确啮合条件是:两轮的()和()必须分别相等。