单项选择题 Depths in the routes (Malacca and Singapore Straits) vary between 20m and about 23m but there are many areas of sand waves and depths are liable to change. The statement infers that（）.

单项选择题 The lifeboat is constructed of（）

单项选择题 Deep-draught vessels and VLCCs shall allow for（）of at least 3.5 m at all times during the entire passage through the Straits of Malacca and Singapore.