Answer: Option (d) is the correct answer.
Explanation:
A reaction in which there occurs change in oxidation state of reacting species is known as an oxidation-reduction reaction.
(a)
Will be written as:

In this reaction, there occurs no change in oxidation state of reacting species. Hence, it is not an oxidation-reduction reaction.
(b) 
Will be written as:

Similarly here, there occurs no change in oxidation state of reacting species. Hence, it is not an oxidation-reduction reaction.
(c) 
Will be written as:

Here, also there occurs no change in oxidation state of reacting species. Hence, it is not an oxidation-reduction reaction.
(d) 
So, here there occurs change in oxidation state of Mg from 0 to +2 and oxidation state of H changes from +1 to 0. Hence, it is an oxidation-reduction reaction.
Thus, we can conclude that
is an oxidation-reduction reaction.
When alpha particles are used to bombard gold foil, most of the alpha particles pass through undeflected. This result of the experiment indicates that most of the volume of a gold atom consists of unoccupied spaces. This was an experiment done by Ernest Rutherford which allowed him to verify the presence of the a small region positive charge in an atom which is called as the nucleus of the atom. Most of the alpha particles pass through the foil while a certain amount were deflected. Those that pass through confirmed that there is a large area that is unoccupied in an atom.
Answer:
The answer is D. It changes the final products of the reaction. .
Explanation:
- <u>. Catalyst is a substance that increases the rate of a reaction without itself being consumed.</u>