8. The alkali metals form salt-like hydrides by the direct synthesis at elevated temperature. The thermal stability of these hydrides decreases in which of the Following orders? (2008)
(a) NaH > LiH > KH > RbH > CsH
(b) LiH > NaH > KH > RbH > CsH
(c) CsH > RbH > KH > NaH > LiH
(d) KH > NaH > LiH > CsH > RbH