Imagine you are a citizen of Athens, enjoying a warm Mediterranean night in the Theater of Herodes Atticus. You are wearing jeans and a T-shirt, listening to a great concert. Now rewind this picture 1,839 years. You are in the same seat, only you are watching classical Greek entertainment and wearing a simple chiton, or tunic. The city of Athens is a fun mix of the old and the new, the classic and the modem. Often a little shop is located next to the ruins of a temple, which is only a block from a large, air-conditioned hotel. The great city of 2,500 years ago is still visible today. Ruins are the most obvious sign of ancient Athens, and the most famous of these is the Acropolis. The Acropolis is a large hill that was the center of life in Athens. On its slopes were temples, monuments, and theaters. From the top, you can see how the urban sprawl (扩展，延伸) of Athens stretches out in every direction. On the top of the Acropolis is the Parthenon. This was once a huge temple to Athena, the city’s patron. It was first completed in 432 B.C., but has been damaged and destroyed several times. However, visitors can still see the "tricks" used in building the Parthenon. The columns along the outside lean inward, and are slightly fatter in the middle. The temple is also higher in the middle than on the sides. All these effects make the Parthenon look perfectly straight from a distance. Only a block away from the Acropolis is the neighborhood of Plaka. The area, with its little shops and restaurants, is very popular with both tourists and locals, and is an important part of modem Athenian culture. Many great thinkers, writers, and political leaders lived in ancient Athens. The ruins of their homes and favorite spots are scattered throughout the busy port city. The hill where St. Paul addressed early Christian Athenians is located near the Acropolis. Great thinkers such as Perikles and Demosthenes spoke to the civil assemblies held at the Pnyx Hill. Today the Pnyx is an open-air theater for light and sound shows. Greeks still use some ancient sites, such as the Pnyx and the Theater of Herodes Atticus. During Roman times, in 76 A.D., gladiators (角斗士) used the Panathenaic Stadium for contests. The Olympics were held there in 1896, and today people still jog and exercise in the stadium. Tourism is very important to people who live in modem-day Athens. Thousands of people come every year to see these ruins and to tour the many museums that house artifacts from ancient times. This provides many jobs and brings money into Athens, which helps the city pay for improvements. Athenians take pride in the accomplishments of their ancestors, and people from all around the world come to admire them. By looking around the city today, we can imagine what life was like in ancient Athens. According to the context, "tricks" in Paragraph Five refer to

A. mischievous acts.
B. confusing constructing skills.
C. skillful constructing methods.
D. constructing materials.