Here’s some ideas to help you on what to write about:
1. Describe what you are involved in, clubs, sports, hobbies, etc!
2. Tell your principal about your accomplishments
3. Tell your principal about your goals and how you plan to accomplish them
Answer:
A. The results of the experiment showed a quantifiable decrease in oxygen levels.
Explanation:
The chosen sentence possesses a formal register with technical vocabulary related to science, which can be understood by professional scientists. For instance, the words <em>quantifiable </em>and <em>decrease </em>have a more academic style. Besides, the writing is impersonal and written in the third person.
The rest of the options are incorrect because they have contractions and they are too informal. Thus, their vocabulary contain casual expressions which do not follow the conventions of an academic style.