单项选择题
What happens to the efficiency of an anchor when it is moved from sand to mud?（）
A.The efficiency increases B.The efficiency decreases C.The efficiency remains the same D.The efficiency cannot be determined.
单项选择题 What form of ice is of land origin?（）
单项选择题 What does the term TO NAVIGATE WITH CAUTION mean?（）.
单项选择题 What are symptom(s) of a ruptured appendix?（）
