Metal hydrides are ionic, convalent or molecular in nature. Among LiH. NaH, KH, RbH and CsH, the correct order of increasing ionic character is:
(a) LiH > NaH > CsH > KH > RbH
(b) LiH < NaH < KH < RbH < CsH
(c) RbH > CsH > NaH > KH > LiH
(d) NaH > CsH > RbH > LiH > KH