Which of the following solutions has the highest $pH$?

$600 \, mL$ of $0.01 \, M \, HCl$ is mixed with $400 \, mL$ of $0.01 \, M \, H_2SO_4$. The $pH$ of the mixture is $....... \times 10^{-2}$. (Nearest integer) [Given $\log 2 = 0.30, \quad \log 3 = 0.48, \quad \log 5 = 0.69, \quad \log 7 = 0.84, \quad \log 11 = 1.04$]

Assuming that $Ba(OH)_{2}$ is completely ionised in aqueous solution under the given conditions,the concentration of $H_{3}O^{+}$ ions in $0.005 \, M$ aqueous solution of $Ba(OH)_{2}$ at $298 \, K$ is $..... \times 10^{-12} \, mol \, L^{-1}$. (Nearest integer)

Following solutions were prepared by mixing different volumes of $NaOH$ and $HCl$ of different concentrations:
$a. \; 60 \; mL \; \frac{M}{10} \; HCl + 40 \; mL \; \frac{M}{10} \; NaOH$
$b. \; 55 \; mL \; \frac{M}{10} \; HCl + 45 \; mL \; \frac{M}{10} \; NaOH$
$c. \; 75 \; mL \; \frac{M}{5} \; HCl + 25 \; mL \; \frac{M}{5} \; NaOH$
$d. \; 100 \; mL \; \frac{M}{10} \; HCl + 100 \; mL \; \frac{M}{10} \; NaOH$
$pH$ of which one of them will be equal to $1$?

$A$ solution with $pH = 5.0$ is diluted $100$ times. Calculate the $pH$ of the diluted solution.

The $pH$ of a $0.005 \ M \ H_2SO_4$ solution will be: