The alkali metals form salt like hydrides by the direct synthesis at elevated temperature. The termal stability of these hydrides decreases in which of the following orders ?
A. NaHgtLiHgtKHgtRbHgtCsH
B. LiHgtNaHgtKHgtRbHgtCsH
C. CsHgtRbHgtKHgtNaHgtLiH
D. KHgtNaHgtLiHgtCsHgtRbH