The correct answer is C.

I) Incorrect-the author says “The clock is a very old invention,” he does not state that the clock is people’s oldest invention.

II) Incorrect. While the para states that “Sundials were used in ancient times,” there is no mention of whether it was the oldest type of clock.

III) Correct. The author states that “Mechanical clocks appeared in the 13th century in Europe. They work with a system of moving gears.”