Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the questions.

The Eiffel Tower is a very famous tower in Paris, France. It was named after the engineer who designed it, Alexandre Eiffel. The tower was built in 1889.

Alexandre Eiffel was asked to build the tower when France decided to have a big fair to exhibit its goods and wares. The tower was located in the middle of the fair as a special attraction. When the structure first started to take shape, the people of France did not like it. They thought it looked like a giant skeleton and was not attractive at all. However, when the tower was finally completed and lighted up at night, the people quickly changed their minds. It was an enchanting sight and now looked like a tower made of lace.

The Eiffel Tower is sometimes considered one of the seven wonders of the modern world. It is 300 meters high and people can take an elevator all the way to the top. From the tower, they can get a marvelous view of the city and the River Seine which runs through it.

The reason ____________ he left was that he felt lonely. A. which B. what C. why D. how