Original sentence: In our Solar System, JUPITER is the biggest and MERCURY is the smallest.
Correct sentence: In our Solar System, Jupiter is the biggest planet and Mercury is the smallest planet.
Step-by-step (easy words):
- Planet names need only the first letter big. So write Jupiter and Mercury, not all big letters.
- Start with the phrase In our Solar System, so put a little comma after it.
- Saying planet makes the meaning clear: biggest planet and smallest planet.
Short spoken version you can say out loud: Jupiter is the biggest planet. Mercury is the smallest planet.