Galileo Galilei was a famous Italian astronomer and scientist who is known for which of the following contributions to science and measurement?

Introduction / Context:
This question tests your knowledge of important scientists and their key discoveries. Galileo Galilei is a central figure in the history of astronomy and physics. Many exam questions ask about his contributions to telescopes, planetary observations, and principles of motion and time measurement.

Given Data / Assumptions:

• The question is about Galileo, an Italian astronomer.
• Options list different achievements, including satellites discovery, development of the telescope, and work on pendulum motion.
• We need to identify which statements correctly describe his contributions.

Concept / Approach:
Galileo improved the design of the telescope, used it to observe celestial bodies, and discovered the four largest satellites of Jupiter, not Mars. He also studied the motion of pendulums and recognised that their regular swing could be used to measure time. Therefore, statements about developing the telescope and linking pendulum motion to time measurement are correct, while the reference to satellites of Mars is inaccurate.

Step-by-Step Solution:
Step 1: Identify the incorrect detail: Galileo discovered four large moons of Jupiter, not Mars.Step 2: Confirm that he significantly improved telescopes and used them for astronomical observations, so the telescope statement is correct.Step 3: Recall that Galileo studied the regular swinging of pendulums and recognised their potential for timekeeping, making the pendulum statement correct.Step 4: Evaluate the combined option “Both B and C”, which groups telescope development and pendulum time measurement.Step 5: Select “Both B and C” as the correct answer, since these two statements correctly summarise Galileo’s contributions mentioned here.

Verification / Alternative check:
Standard science history texts describe Galileo’s major achievements: his telescope work, observations of Jupiter’s moons, and investigation of pendulum motion. None of these sources attribute the discovery of satellites of Mars to him; those were discovered later by other astronomers. This confirms that only the telescope and pendulum statements in the options match Galileo’s verified contributions.

Why Other Options Are Wrong:
Discovered four satellites of Mars: Incorrect, since Galileo observed moons of Jupiter, not Mars.Developed the telescope: Correct, but incomplete when chosen alone, because the question points to multiple contributions.Discovered that pendulum motion can measure time: Correct, but again incomplete alone.

Common Pitfalls:
Some students may quickly pick a single correct statement instead of the combined option, or may misremember which planet’s satellites Galileo discovered. It is important to read each choice carefully and verify every detail, especially when combined options such as “Both B and C” are present. Linking each scientist with a clear set of achievements can help avoid confusion.

Final Answer:
Galileo is correctly associated with developing the telescope and recognising pendulum motion as a regular timekeeper, so the right choice is Both B and C.