Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: The Himalayan Mountain chain is the youngest and tallest mountain chain on Earth. Which phenomenon contributed most to this area of continental buildup?
convergence of continental plates
Indo-Australian Plate collision with the Eurasian Plate.