Here's a problem to solve: What enabled Galileo in the 17th century to see the moons of Jupiter?

Among the 4 following options, which is the correct answer?

- A: Jupiter came close to Earth during his lifetime.
 
- B: He realized that all of the planets go around the Sun.
 
- C: He invented advanced tools for looking at the sky.
 
- D: Earlier scientists failed to take an interest in the sky.
 