Which of the following molecules is/are chiral?

The correct statement$(s)$ about the compound $H_3C-CH(OH)-CH=CH-CH(OH)-CH_3$ $(X)$ is(are):
$(A)$ The total number of stereoisomers possible for $X$ is $6$.
$(B)$ The total number of diastereomers possible for $X$ is $3$.
$(C)$ If the stereochemistry about the double bond in $X$ is trans,the number of enantiomers possible for $X$ is $4$.
$(D)$ If the stereochemistry about the double bond in $X$ is cis,the number of enantiomers possible for $X$ is $2$.

Which of the following compounds is optically inactive?

Which dimethylcyclobutane is optically active?

How many meso isomers are possible for $2, 3, 4-\text{pentanetriol}$?

The number of chiral carbons present in the molecule given below is......