Which of the following is most basic ? (CPMT 2008)

The bases are the compound which has the ability to donate electron. 2 NO is the electron-withdrawing group, thus reduces the electron density of the compound. Only butamine is the compound where 4- alkyl group and 2 NH increases the electron density of the compound and thus the basicity. Structure of compounds given in option are below Thus, the correct option is (a) Butamine