Which of the following is a lachrymatory agent or tear gas?

What is $\underline{Z}$ in the following sequence of reactions?

Comment on the stereochemistry of the products for the following reaction:
$3$-methylpentan-$2$-one + $CH_3MgBr$ followed by $NH_4Cl$ workup.

In the above sequence,$P$ and $Q$ products can be distinguished by?

Consider the above reaction,the major product $'P'$ is:-

$CCl_3CHO \xrightarrow[KOH]{Conc.}$ Main product is