Number of stereoisomers (including enantiomers and meso forms) is/are correct?

Option A: butane-2,3-diol has two like stereocentres in a symmetric skeleton, giving the $(R,R)$ and $(S,S)$ enantiomeric pair plus the achiral meso $(R,S)$ form, which makes three, so A is correct. Option B: 1,3-dimethylcyclohexane has two stereocentres ($\mathrm{C_1}$ and $\mathrm{C_3}$); the cis isomer has an internal mirror plane and is meso, while the trans isomer is chiral and exists as a pair of enantiomers, giving three, so B is correct. Option C: in the 1,4-isomer both substituted carbons lie on a mirror plane, so there are only cis and trans, both achiral, giving two, so C is wrong. Option D: the symmetrical diene has $(E,E)$, $(Z,Z)$ and $(E,Z)$ forms, and the $(Z,E)$ form is identical to $(E,Z)$, giving three, so D is correct.