Read the following passage and mark the letter A, B, C, or D to indicate the best option for each of the blanks.

Why do people like to chew gum? Some people say they like the taste. (46) ________say they can think better if they chew gum. Some people chew it when they have some boring work to do. Others chew gum when they are nervous.

Gum is a mixture of things. For many years gum companies made gum from chicle. Chicle is a natural gum from a tree in Mexico and Central America. Now companies use plastic and rubber made from petroleum (47) ________of chicle.

Gum must be soft so that you can chew it. A softener keeps it soft. The gum company makes the softener from vegetable oil. A sweetener makes the gum sweet. The sweetener is usually sugar. Then the company (48) ________the flavor.

Thomas Adams made the first gum from chicle in 1836. However, chewing gum was not new. The Greeks chewed gum from a tree (49) ________2,000 years ago. Mayan Indians in Mexico chewed chicle. Indians in the Northeastern United States taught Europeans to chew gum from a tree there.

People first made bubble gum in 1928. Children like to (50) ________bubble with bubble gum. Some university students do too.

Điền vào câu 50