What Is the Hydronium-Ion Concentration in a Solution Formed by Combining

Multiple Choice

What is the hydronium-ion concentration in a solution formed by combining 750 mL of 0.10 M NaOH with 250 mL of 0.30 M HCl?
NaOH(aq) + HCl(aq) $\to$ NaCl(aq) + H₂O(l)

A) 0.075 M
B) 1.7 $\times$ 10^-13 M
C) 1.0 $\times$ 10^-7 M
D) 0.30 M
E) 0.10 M