Here is an article from an exam.
Imagine if just anybody could hike up the tallest mountain in the world and be back again in time for dinner, with no special equipment or training needed. Well, perhaps they can, because it seems that when it comes to measuring mountains the playing field is far from level. Traditionally, mountains have been measured from sea level to peak. So Mt Everest, with a peak 8848 meters above sea level, is undoubtedly the tallest. Expeditions to Everest take huge effort.
But what about mountains that do not begin at sea level? If we were to measure mountains from top to bottom, then the tallest mountain on Earth would be Mauna Kea on the island of Hawaii. Measured from sea level, Mauna Kea is only 4207 metres tall, but the base of Mauna Kea lies deep down on the floor of the pacific Ocean. From top to bottom, Mauna Kea stands a huge 10210 metres tall. Preparing for that expedition is a lot more civilised. It is an 8-hour trip from the Mauna Kea visitor centre to its summit, and you can even drive all the way to the top.
What is the meaning by the quotation, "when it comes to measuring mountains the playing field is far from level"
A) it is not possible to measure mountains that are not side by side
B) The mountains have not been measured accurately
C) It is not useful to compare the heights of mountains
D) There is more than one way to describe how tall a mountain is
(Edit) From Wikipedia:
.. a level playing field is a concept about fairness, not that each player has an equal chance to succeed, but that they all play by the same set of rules.
However it is not clear how this applies to mountains. Could someone please explain which would be the correct answer choice?