<u>Answer:</u>
<em>Atomic number 75 is dedicated to an element named rhenium and has been given Re as its chemical name.</em>
<u>Explanation:</u>
With a really low concentration it is one of the rarest metals that is found in Earth's crust.
Like all other elements rhenium also has certain isotopes among with 185 and 187 are the most stable ones. Hence these two are the ones that are naturally available abundance is 34% and 63% respectively.
Sandy soil because the sand will erode faster then the clay will causeing the well to cave in
There are 115 known elements as of today (Feb. 13, 2016)
so, 'C' is the correct answer
