# The two cleavage reactions are given below :

$\begin{array}{1 1}(a)\;\text{The reagent used in reaction (I) is anhydrous HI in ether and in reaction(II) is concentrated HI}\\(b)\;\text{The reagent used in both reactions (I) and (II) is ahydrous HI in ether}\\(c)\;\text{The reagent used both in reactions (I) is conc.HI and in reaction (II) is anhy.HI in ether}\\(d)\;\text{Above all statements are correct}\end{array}$

The solvent also plays important role on deciding the formation of products
In ether
$(CH_3)_3COCH_3\quad\underrightarrow {anhyd.HI}\quad CH_3I+(CH_3)_3COH$($SN^2$ mechanism)
In water
$(CH_3)_3COCH_3\quad\underrightarrow{Conc.HI}\quad CH_3OH+(CH_3)_3CI$($SN^1$ mechanism)
Hence (a) is the correct answer.