Give the products with their stereoisomers, if any.
`a.`
`b.`
`c.`

Explanation

`a.`
`b.` Note: Metal `+H_(2)` does not reduce `(R-X)` to `(R-H)` but reduces `(Ar-X)` to `(Ar-H)`.
Reactant is cis `+` mechanism of addition is syn `rarr` product is meso.

`c.` Reactant is trans `+` mechanism of addition is syn `rarr` product is `dl` or `(+-)` racemic.

`d.` Reactant is cis `+` mechanism of addition is syn `rarr` product is meso.

Meso`-1,2-`dymethyl cyclohexane `(O.I.A.)`
`e.` Reactant with two different groups `+` mechanism of addition is syn `rarr` product is `dl` or `(+-)` or racemic.
`dl-2,3-` Dibromopentane
`f.` Reactant is cis with two different groups `+` mechanism of addiciton is syn `rarr` product id `dl` or `(+-)` or racemic.
dl`-2,3-`Dibromopentane
`g.` Reactant is cis `+` meachanism of addition is syn `rarr` product is meso.

`h.` Reactant is trans `+` mechanism of addition is syn `rarr` product is `(+-)` or `dl` or racemic.
`dl-2,3-`Dideutereo`-` butane
`i.` Reactant cis or trans `(` with different groups `)+` mechanism of addiction is syn `rarr` Product is always `(+-)` or `dl` or racemic.

As there are two different groups in the alkene, the plane of symmetry is not attained. So the product is never obtained in meso from but optical isomers `d` and `l` are obtained from cis `-` or trans `-` alkene.
`j.`
Both reactions are catalytic hydrogenation. Reation `(1)` is heterogenous catalytic hydrogenation in which the solid catalyst is in a different phase from the reactant `(A)(` gas phase `).` Reaction `(2)` is homogenous cataytic hydrogenation because the reactant and the catalyst are in the same gaseous phase.