- AKetone
- BEster
- CAmide
- DEther
Explanation:
Box a encloses ester group, b encloses ketone group while c encloses amide group.
Here ether group is not present.

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Reason : $sp$ hybridised carbon atoms of acetylene are considerably electronegative.

$MnCl _2+ K _2 S _2 O _8+ H _2 O \longrightarrow KMnO _4+ H _2 SO _4+ HCl$ (equation not balanced).
Few drops of concentrated $HCl$ were added to this solution and gently warmed. Further, oxalic acid ( $225 mg$ ) was added in portions till the colour of the permanganate ion disappeared. The quantity of $MnCl _2$ (in $mg$ ) present in the initial solution is. . . . . . . . . (Atomic weights in $g mol ^{-1}: Mn =55, Cl =35.5$ )