Ocean trenches such as the Tonga and Marianas Trench, are A) ...

[tth]

Ocean trenches such as the Tonga and Marianas Trench, are
 
  A) subduction zones where lithosphere is pulled down to the asthenosphere.
  B) some of the steepest places on Earth.
  C) found at continental-continental plate boundaries that mark the the deepest places on Earth.

Question 2

Where do the ocean's salts originate?
 
  What will be an ideal response?

[macagn]

Answer to Question 1

Answer: A

Answer to Question 2

Answer: One source is the chemical weathering of continental rocks. As rocks weather, elements such as sodium, calcium, and potassium dissolve into the water that flows downstream to eventually make its way to the ocean. Earth's interior is another source. Throughout Earth's history, volcanic eruptions have delivered huge quantities of chlorine, as well as water vapor and other gases, to the ocean. Chlorine plus sodium? Sodium chloridecommon table salt. Hence, the ocean's salty taste.

[tth]

Both answers were spot on, thank you once again

[macagn]

Great! Please up vote