Question

what effect does an increase in concentration of H+ ions in a solution have on the pH of the solution?

Answer 1

if we add any substance which have hydrogen atoms in that solution then it will obviously and compulsory increase the concentration of h + ions in the solution

Oh I got it wrong.
Increase in h+ion concentration will decrease pH as it is - log(h+).

Answer 2

if there is increase in concentration of h+ ions in solution then its ph starts decreasing and it makes solution more acidic than before.
I HOPE IT HELPS