A. actinides do not occur in nature.
Any buffer exists in this equilibrium
HA <=>

In a buffer, there is a large reservoir of both the undissociated acid (HA) and its conjugate base (

)
When a strong acid is added, it reacts with the large reservoir of the conjugate base (

) forming a salt and water. Since this large reservoir of the conjugate base is used, the ph does not alter drastically, but instead resist the pH change.
Protons cannot be lost without the atoms becoming an entirely different element. Elements can infact have different numbers of neutrons within the same element, but neutrons are not related to the electrical charge. The answer is c. electrons.
The high surface tension helps the paper clip - with much higher density - float on the water. The property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules.
Basically it means that there is a sort of skin on the surface of water where the water molecules hold on tight together. If the conditions are right, they can hold tight enough to support your paper clip. The paperclip is not truly floating, it is being held up by the surface tension.
I can’t see the picture where’s it at