Which of the following compounds is the weakest Bronsted base?

1.                 2.              3.    4.          

HINT- Least tendency to donate electron pair and least tendency for acceptance of proton is weakest base
EXPLAINATION (3) Phenol is the weakest Bronsted base as its lone pair is in conjugation with the ring .And also
Oxygen is more electronegative than N. So, the O—H bond is more polar and it has the highest value of acidic character. Since phenol is more acidic than aniline,So phenol is the least basic among the given four choices.In  cyclohexane derivatives lone pair is free.so they are stronger base than benzene derivatives