Arrange the following in decreasing order of basic strength (I) CH3CHTMgBr                   (II) H-C≡CMgBr(III) CH3CH2OMgBr

The best way to compare their basic strength is to compare the acidic strength of their conjugate acid and then reverse the orderbecause there is inverse relation in the strength of conjugate pair. The order of acidic strength of conjugate acid is CH3CH2OHCH3CH3∴Decreasing order of basic strength isCH3CH2−>H−C≡C−>CH3CH2O−