One of his greatest achievements was the (9) ______ of the three laws of motion which are still used today.

Read the passage and mark A, B, C, or D to indicate the correct answer to each of the blanks from 9 to 13

Sir Isaac Newton, the English scientist and mathematician, was one of the most important figures of the 17^th century scientific revolution. One of his greatest achievements was the (9) ______ of the three laws of motion which are still used today. But he also had a very unusual personality. Some people would say he was actually insane. 

His father died before he was born, and his mother soon remarried. The young Isaac hated his stepfather so much that he once (10) _______ to burn his house down - when his stepfather and mother were still inside! Fortunately, he did not, and he went on to graduate from Cambridge without being thrown into prison. Isaac's first published work was a theory of light and color. When another scientist wrote a paper criticizing this theory, Isaac flew into an uncontrollable rage. The scientist responsible for the criticism was a man called Robert Hooke. He was head of the Royal Society, and one of the most respected scientists in the country. (11) ________, this made no difference to Isaac, (12) _______ refused to speak to him for over a year. 

The simple fact was that Isaac found it impossible to have a calm discussion with anyone. As soon as someone said something that he disagreed with, he would lose his temper. For this reason he lived a large part of his life isolated from (13) _______ scientists. It is unlikely that many of them complained.

(Source: https://www.biography.com/scientist/isaac-newton)

(9) __________

• A. discovery
• B. findings
• C. research
• D. inventions