Indicator for the titration of $HCl$ and $Na_2CO_3$ would be

$A$ $0.1 \ N$ solution of $Na_2CO_3$ is titrated with $0.1 \ N$ $HCl$ solution. The best indicator to be used is

Which indicator is most suitable for the titration of $0.1 \, N \, Na_2CO_3$ solution with $0.1 \, N \, HCl$?

For an acid indicator with $K_{in} = 1.0 \times 10^{-5}$, the color change occurs when the concentration of the indicator is $1 \times 10^{-3} \ M$. Find the $pH$ at which the color change occurs.

$50 \ mL$ of $0.1 \ M$ of a weak acid $HA$ is titrated with $0.1 \ M$ of $NaOH$. The ionization constant of $HA$ $(K_a)$ is $1.8 \times 10^{-5}$. Using the given information and from the options shown below,the best indicator for the titration of $HA$ with $NaOH$ is $....$

Which indicator is used for the titration of a weak acid (oxalic acid) and a strong base (caustic soda)?