The order of nucleophilicity of halides in aqueous solution is

Arrange the following compounds in the order of decreasing reactivity towards electrophilic substitution reaction.

($\mathrm{I}$) 

($\mathrm{II}$) 

($\mathrm{III}$) 

($\mathrm{IV}$) 

Give the order of decreasing reactivity towards an electrophile.

$1.$ 

$2.$

$3.$

$4.$

$5.$

Examine the relation between the following pairs of compounds.

Which of the following statements are true about urea?

I. Urea is the first organic compound which is synthesised in the laboratory.

II. Urea is the best water-soluble nitrogenous fertilizer.

III. Urea leaves only ${\mathrm{CO}}_2$ after ammonia has been assimilated by plants.

Which of the following is NOT a nucleophile?