What is $X$ in the given reaction?
$HOCH_2-CH_2OH + (COOH)_2 \xrightarrow{210^{\circ}C} X$
(major product)

Which of the following reacts with $KMnO_4$ but does not react with $AgNO_3$?

With anhydrous zinc chloride,ethylene glycol gives:

An alkene $A$ (molecular formula $C_{5}H_{10}$) on ozonolysis gives a mixture of two compounds $B$ and $C$. Compound $B$ gives a positive Fehling's test and also forms iodoform on treatment with $I_{2}$ and $NaOH$. Compound $C$ does not give Fehling's test but forms iodoform. Identify the compounds $A, B$ and $C$. Write the reaction for ozonolysis and the formation of iodoform from $B$ and $C$.

Identify the major product $X$ in the following reaction:
$1,5,5-\text{trimethylcyclohex-1-ene} \xrightarrow{N.B.S., h\nu} X$

Which of the following alkenes is the most stable?