UnScramble this Word: n e c e s u i r?

Questions

The Hawaiian Islands are the projecting tops of the biggest mountain range in the world. Mauna Kea, on the island of Hawaii, is the largest mountain on Earth - though partially submerged, it is 4,000 feet taller than -----------------?

The highest mountain in the British Isles, Ben Nevis in western ----------, is just 4,406 feet high. In many other countries, a "mountain" of this size would be considered something less than a large hill.?

The highest mountain on Earth, -------------, reaches only about halfway through the lowest layer of the troposphere.?

There are sand dunes in Arcachon, ----------- that are 350 feet high.?

The highest point in Pennsylvania is lower than the lowest point in --------------?