H2SO4 is a strong acid, so it will completely dissociate into corresponding ions.
On dissociation, H2SO4 → 2H+ + SO42−
If the concentration of H2SO4 is 0.001 M so, the concentration of 2H+ will be 0.002 M (0.001 x 2). This is because 1 molecule of H2SO4 gives 2H+ ions.
Recall that pH = - Log10[H+]
pH = - Log10[2H+] (basicity is 2)
= - Log10[2 x 0.001]
= - (Log102 + Log10 0.001)
= - (Log102 + Log10 10−3)
Also recall that Log102 = 0.3 and Log1010 = 1
Therefore, pH = - (0.3 - 3)
= - ( - 2.7)
= 2.7 - Option A