<span>The alkali metals and hydrogen are reactive because they have only one electron to give in order to complete their valence shell. It is easier to give that one electron so when given the opportunity they will. This means they will react with anything polar or willing to take an electron.</span>
Explanation:
I hope you interested about the chemical what they add in tea
Buffer is formed from weak acid and its salt with strong base (its conjugate base)
So the only one correct answer is :
0.2 M H₃PO₄ and 0.2 M NaH₂PO₄
While all other choices are incorrect