The correct order of reativity of $P h M g B r$ towards given compounds.
$P h - O | | C - P h$ $C H_{3} - O | | C - H$ $C H_{3} - O | | C - C H_{3}$
(I) (II) (III)

(I) > (I I) > (I I I)

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(I I I) > (I I) > (I)

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(I I) > (I I I) > (I)

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(I) > (I I I) > (I I)

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Solution

The correct option is B $(I I) > (I I I) > (I)$
$i i > i i i > i$
Since alkyl group has $+ I$ effect and aryl group has $+ R$ effect, thus, greater the number of alkyl and aryl groups attached to the carbonyl group, its' reactivity towards neucliophilic addition reaction decreases secondly, as the steric hindrance on carbonyl group increases the reactivity decreases accordingly.
$C H_{3} - O | | C - H > C H_{3} - O | | C - C H_{3} > P h - O | | C - P h$

Among aldehydes and ketones, aldehydes are more electrophilic as in ketones the charge on carbonyl carbon is decreased by $+ I$ effect of both alkyl group.

Also the tetrahedral intermediate of aldehydes have less steric repulsion.

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I

I I

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