A fuel-air mixture below the lower explosive limit is too（）.
A. rich to burn
B. lean to burn
C. cool to burn
D. dense to bur
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课堂教学要想取得预期的效果，就必须以恰当的（）。
A. 课堂常规为基础
B. 课堂管理为基础
C. 课堂学习为基础
脱氢氰酸塔的作用是出去丙烯腈中所含的氢氰酸及水分。
A. 正确
B. 错误
A fire is discovered in the forepeak of a vessel at sea. The wind is from ahead at 35 knots. You should（）.
A. remain on course and hold speed
B. change course and put the stern to the wind
C. change course to put the wind on either beam and increase speed
D. remain on course but slack the speed
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