Answer:
The answer would be C: As Tina's skill at studying increased, her grades improved.
Explanation:
Since Tina is the only noun here owning something, and she is a singular object, using one apostrophe before the S is the correct answer
2. talking in a friendly way - chatting
3. <span>describes a person who chooses carefully - selective
4. not having something - without
5. describes a person who knows 100% that something is sure - sure
6. do something once to see if it is good - (you didn't provide an option for this, might be something like: try or test)
7. use (v) - spend
8. once a year (adj) - annual</span>
