1. Which among the following can serve as buffer system for a solution with pH = 3.0?

2. Which among the following has the highest acidity?

3. Which among the following has the highest pH?

\begin{tabular}{|l|l|l|} \hline Name & Formula & Kat \\ \hline Ascorbic & H2C6H6O6 & 8.0105 \\ \hline Carbonic & H2CO3 & 4.3107 \\ \hline Citric & H3C6H5O7 & 7.4104 \\ \hline Oxalic & HOOCCOOH & 5.9102 \\ \hline Phosphoric & H3PO4 & 7.5103 \\ \hline \end{tabular}