Last one is more acidic than other but it shows + i effect, so how it becomes more acidic?

first three show +H effect and +H effect decrease from I>II>III and last one i.e., show only +I effect because it's doesn't have any alpha H. we know that Hyperconjugation is domin...

Even though the tert-butyl group has greater +I effect, one needs to remember that these alkyl groups have hyperconjugable hygrogen atoms. The electron donating effect through hype...