Answer:
Mrs. Tremont has several students who love her science class.
Several of her students' projects won ribbons at the science fair.
One student's invention was awarded the first place trophy.
Step-by-step explanation:
The first sentence refers to a plural noun, which is indicated by the word several. That is why the plural form of the noun student is used, without possessive case.
The second sentence describes the projects done by several students, so the plural noun students is used with an apostrophe, indicating possessive case.
Finally, the last sentence concerns one single student whose invention received a prize. Thus, the words one, invention and was demonstrate that the sentence refers to one person.