-p-Block elements - I — Chemistry STD 11 Science — Question

[Given : $p K _{ a 1}$ and $p K _{ a 2}$ of $H _2 CO _3$ are $6.37$ and $10.32 $, respectively $; \log 2=0.30$ ]

$(I)$ $\phi -CH_3$

$(II)$ $\phi -CH_2-CH_3$

$(III)$ $\phi -CH(CH_3)_2$

$(IV)$ $\phi-C(CH_3)_3$

towards electrophilic substitution will be - [where $\phi =C_6H_5$]