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

While few people claim to be addicted to it, ice cream is certainly a great favourite among people of all ages in many parts of the world. Although it is commonly believed to have originated in China, and has long been associated with Italian manufacturers, it doesn't actually come from either of those countries. Ice cream originated when chemists in the Middle East worked out that adding salt to water reduces its freezing point, making it possible to cool it below its normal freezing point without turning it to ice.

Folklore also holds that Nero, the Roman Emperor, invented water ice during the first century AD when he sent slaves up in the mountains and made them pass buckets of snow, hand over hand, to his banquet hall, where it was mixed with honey and wine. However, there is nothing to prove that tale.

Well, one way or another, the method for making this delicacy found its way into Europe. The first book to mention it was published in Italy in 1530. At that time, water ices were typically served by monarchs and other important people as a special treat on great occasions. The British are supposed to have been responsible for coming up with the idea of using cream in their ices instead of plain water, and thus ice cream as we know it today was born.

Scientists are now beginning to carry out experiments on ________________ trigger different sorts of health risk. A. noise pollution can B. that noise pollution C. how noise pollution D.