Which of the following ions will affect the pH of an aqueous solution? Al+3 Br- Na+ NO3-?

Al³⁺ ion will affect the pH of an aqueous solution.

Actually, Al³⁺ ion exists as [Al(H₂O)₆]³⁺ in aqueous solution.
Al³⁺(aq) + 6H₂O(l) → [Al(H₂O)₆]³⁺(aq)

As Al³⁺ ion is very small and carries 3 positive charges, its charge density is very high. Therefore, Al³⁺ ion can polarize the surrounding H₂O molecules (i.e. distort the electron clouds of H₂O molecules), and the H-O bonds in H₂O molecules would be weakened and some O-H bonds will thus be broken to give H⁺ ions.
[Al(H₂O)₆]³⁺(aq) →[Al(H₂O)₅(OH)]²⁺(aq) + H⁺(aq)

Due to the presence of H⁺(aq) ions, pH of the solution increases.

As each ion of Br⁻, Na⁺ and NO₃⁻ carries only one positive or negative charge, the charge density is not high enough to cause the above effect.

...
here's a general rule we may apply

salts of weak acids form basic solutions
salts of weak bases form acidic solutions
the reason is that one of the ions in the salt will undergo hydrolysis

salts of strong acids and bases do not hydrolyze to any appreciable extent
so they are neutral in solution

Al+3 is from a weak base (Al(OH)3) so will form a somewhat acidic solution
the rest of the given ions are from strong acids or bases and will not affect pH

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