In this section, you will hear several passages.
Listen to the passages carefully and then answer the questions that
follow.
Questions 11 to 13 are based on the
following passage. At the end of the passage, you will be given 15 seconds to
answer the questions. Now, listen to the
passage.
What is the purpose of a canal lock
A．To keep out boats that are too large for the canal. B．To measure the tonnage of canal boats. C．To load and unload the cargo. D．To change the depth of the water.