Answer:
The correct answer is C: no, because it jumps to a supporting reason without clearly stating a stance.
Explanation:
Before introducing the main idea of her letter, Roberta should make a brief introduction about the planetarium and list some arguments about why they should visit the planetarium.
This sentence is not a good way to start her letter, as she jumps directly to a supporting reason without clearly stating a stance because some of her classmates could consider her approach too aggressive and inappropriate.
Each letter should consist of an introduction, where the author will expose his/her ideas politely and concisely, and after that, at the main part, the author should develop his propositions and ideas and represent it adequately. Therefore, Roberta should make a proper introduction and then introduce her proposition of visiting the planetarium.