$(+) -$ Tartaric acid and meso-tartaric acid are ........

Which type of isomerism is exhibited by the given compound?
$(CH_3)_2C=CH-CH(CH_3)COOH$

Which of the following compounds is a meso compound?

Optically active isomer $(A)$ of $(C_5H_9Cl)$ on treatment with one mole of $H_2$ gives an optically inactive compound $(B)$. Compound $(A)$ will be:

Identify the chirality of the molecules $X$ and $Y$ shown below:

Which of the following is optically active?