Arrange the carbanions $({\mathrm{CH}}_3{)}_3{\mathrm{C}}^{-}, {\mathrm{Cl}}_3{\mathrm{C}}^{-}, ({\mathrm{CH}}_3{)}_2{\mathrm{CH}}^{-}, {\mathrm{C}}_6{\mathrm{H}}_5{{\mathrm{CH}}_2}^{-}$ in order of their decreasing stability.

The stability of the carbanions in the following is

   (I) $\mathrm{RC}\equiv {\mathrm{C}}^{-}$    (ii)        (iii) ${\mathrm{R}}_2\mathrm{C}=\stackrel{-}{\mathrm{C}}{\mathrm{H}}_2$      (iv)  ${\mathrm{R}}_3\mathrm{C}-\stackrel{-}{\mathrm{C}}{\mathrm{H}}_2$.

The order of the base strength of the compounds is. 

The order of decreasing ease of abstraction of hydrogen atoms in the following molecule is.