4542
The construction of the weir and lock was necessary to protect the new developments on the canal ( the metropolitan railway , the tributary canals and later the harbour and ships ) from floods and ice , but also to maintain sufficient water in the canal so that ships could pass .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
 Entities:  
Answer:
 None