<u>Answer:</u> The correct option is D) 
<u>Explanation:</u>
The oxidation reaction is defined as the reaction in which a chemical species loses electrons in a chemical reaction. It occurs when oxidation number of a species increases.
A reduction reaction is defined as the reaction in which a chemical species gains electrons in a chemical reaction. It occurs when oxidation number of a species decreases.
For the given chemical reaction:

<u>On the reactant side:</u>
Oxidation number of Zn = 0
Oxidation number of Ag = +1
<u>On the product side:</u>
Oxidation number of Zn = +2
Oxidation number of Ag = 0
As the oxidation number of Ag is decreasing from +1 to 0. Thus,
is getting reduced.
Hence, the correct option is D) 
Atoms of elements below atomic number 20 do not split because of stable nucleus.
Stability of nucleus is determined by neutron/proton ratio.
For light stable nuclides, number of protons ans neutrons are same. For heavy nuclides, number of neutrons is more than the number of protons.
Here the type of decay is alpha decay because number of nucleons(protons and neutrons) changes.
Hence option d is correct.
Answer:
17. D. Chemical change
18. C. Cell wall
19. D. To transfer matter and energy within and between organisms.
20. A. Transporting materials
21. C. Carbon dioxide
22. A. Cellular respiration
23. C. Produce food and give off oxygen
Explanation:
I have been able to supply the correct answers. The cell wall functions as a structure that provides structural support and protection to the cell. It is tough, flexible and at times rigid. In a chemical change, new materials with new properties are manufactured. So, the process of photosynthesis is a chemical change.
The endoplasmic reticulum actually transports material. It transports materials like protein and lipids made within the cell and sends it to where they are needed.
Carbon dioxide is the the gas that animals give off and plants use it during photosynthesis. Cellular respiration involves the activities that result to the breaking down of food in order to release energy.
Think of it this way,
Mix Iron and sulphur in a bowl. How do you separate them? Use a magnet right. Yes.
Now, mix the iron and sulphur together but know, heat them up. Let them cool for a while. After that, use a magnet to separate. You cant. This is because the compound (FeS) now has a different property from its original components.
Apply this theory onto salts.
Reduction. B is the correct answer