The correct option is
B II>I>IV>IIIBasic strength
∝ Tendency to donate lone pair.
Now,
`I)`
Here `'N'` bearing lone pair is
sp2 hybridised.
∴ It is more electronegative hence, has less tendency to donate.
`II) `
Here `'N'` is very rich in electron density as it is surrounded by 3
+I groups and also it is
sp3 hybridised.
∴It has a good tendency to donate a pair
e−.
`III)`
Lone pair of
e− on `'N'` are involved in conjugation with 'O' it is a weak base.
`IV)`
Here also lp of `'N'` is involved in resonance with the benzene ring.
∴ the availability of 'lp' here is also less. But it is more compared to case `(III)` as in case `(III)` extent of delocalisation is more.
So, the correct order of basic strength is:
II>I>IV>III