<u>Answer:
</u>
The study carried out by Dr. Xu is a randomized controlled study.
<u>Explanation:</u>
- For the sake of determination of how the results of the students change by doing certain changes to the examination pattern, Dr. Xu devised that the change is considerably evident.
- Dr. Xu provided and intervention in the process of exam in the form of guides which helped the students to score better later. Hence, from the standard of conduct of the study, it can be said to be a randomized controlled study.
I think it is the cell membrane, but there is a possibility it is the cell wall. I think the cell membrane is correct because the skin does allow certain things into your skin cells, such as water. Similarly, cell membranes allow certain things in the cell. The cell membrane basically acts as the security guard of the cell.
4. The discovery of gold and precious metals sparked infrastructure and population growth.
