Which one of the following is the strongest base in aqueous solution?

In aqueous solution, the basic strength of methyl-substituted amines is determined by three factors: Inductive effect ($+I$), Solvation effect (hydrogen bonding with water), and Steric hindrance.The experimental order of basic strength for methyl amines in water is:$2^{\circ }>1^{\circ }>3^{\circ }>\text{Ammonia}$ Dimethylamine ($2^{\circ }$) is the strongest base.Note: Aniline is much weaker because the lone pair on nitrogen is delocalized into the benzene ring.