How is a valley similar to an ocean trench?

there similar because valleys are low points in mountains and hills and in a ocean trench its the like low part of the ocean with high walls surrounding it

Explanation:

there low points lol

answer; i believe that the correct answer is (c) arctic tundra;

answer: the time zones used to be whatever the local authority wanted them to be. one town might have 6am whenever the sun came up and another town had 6am 10 minutes later.  

the trains had a hard time when their orders said to be at a certain point at 6am.  

6am, but who's 6am.  

the railroads got together and set the time zones more or less along the longitude lines across the country.

explanation: