Balloons have been around since time immemorial, yet they have never lost their appeal. Long before scientist Michael Faraday created the first rubber balloon in 1824, humans were inflating pouchesand bags made from various materials. The earliest balloons involved animal bladders, which were known to have been used in ancient Greece. In another early example, the Aztecs put air into cat intestines __1__ they could form them into shapes to offer as sacrificesto the gods. Cloth and canvaswere also used to make balloons.
Although many people associate balloons with celebrations and kids’ playthings, balloons __2__ numerous other applications over the past few centuries as well. Faraday invented his rubber balloons to help with experiments involving hydrogen. In fact, there is a long tradition of using balloons for scientific experimentation. In the late 1800s, a French meteorologistbegan using them to carry __3__ into the air to help with weather measurements. Balloons have also been developed into forms of transportation, including hot-air balloons and Zeppelins. Moreover, they have been deployed for surgicalprocedures __4__ tiny balloons are inserted into the body and used to open blocked blood vesselsnear the heart.
Despite the important uses of balloons and enjoyment people get from them, it is important to note that they can present an environmental problem. Balloons that are released into the air can __5__ the environment, and since they are not biodegradable, they pose a hazard to wildlifethat may ingest them. While we enjoy the beauty of balloons, we need to take into consideration the impact they may have on nature.
1. (A) unless (B) though (C) so that (D) in case
2. (A) have (B) are having (C) have had (D) were having
3. (A) instruments (B) arrangements (C) documents (D) garments
4. (A) to whom (B) in which (C) by what (D) at that
5. (A) decorate (B) confront (C) scatter (D) litter
