VITEEE 2014 Paper

In case of CH3COO− and NCCH2− negative charge is involved in conjugation so less available for donation. While in case of C2H5SH and CH3NH2 both nitrogen and sulphur have lone pairs but sulphur is less electronegative than nitrogen hence sluphur lone pairs are more available for more donation. So C2H5SH is strongest nucleophile.