Which of the following are meso compounds?

The number of possible isomers for the molecular formula $C_2H_3Cl_3$ is...........

$Propanone$ and $propanal$ are:

The two compounds $CH_3-CH_2-C(=O)-CH_2-CH_2-CH_3$ and $CH_3-C(=O)-C(CH_3)_2-CH_3$ can be classified as:

Identify the pairs of compounds that represent chain isomerism among the following:
$I. CH_3-CH_2-CH_2-CH_2-OH$ (Butan$-1-$ol)
$II. CH_3-CH_2-CH(OH)-CH_3$ (Butan$-2-$ol)
$III. (CH_3)_3C-OH$ ($2$-Methylpropan$-2-$ol)
$IV. (CH_3)_2CH-CH_2-OH$ ($2$-Methylpropan$-1-$ol)

Provide the structures of chain isomers of $C_6H_{14}$ that contain two methyl groups,along with their $IUPAC$ names.