Câu hỏi:

Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct option to each of the questions that follow.

Glass fibers have a long history. By 1600 B.C., the Egyptians were producing coarse fibers, and as early as 1375 B.C., fibers were used as ornaments on Egyptian pottery. Glassmakers in Venice employed glass fibers to adorn the exterior of simple glass vessels throughout the Renaissance, which took place in the fifteenth and sixteenth centuries A.D. But glassmakers were so secretive about their trade that no one wrote about the creation of glass fiber until the early seventeenth century.

     During the seventeenth century, "spun glass" fibers were created. French physicist Rene-Antoine de Reaumur attempted to create glass feather substitutes. By spinning a wheel into a puddle of molten glass and plucking glass threads where the hot, viscous liquid adhered to the wheel, he created fibers. Despite the short and delicate nature of his fibers, he anticipated that spun glass threads as thin as spider silk would be flexible enough to be woven into textiles. Glassmakers discovered at the beginning of the nineteenth century that using a hot glass tube to extract fibers from molten glass produced longer, stronger fibers. The creators wrapped a yarn reel with the cooling end of the thread and quickly spun it to extract additional fiber from the molten glass. At fairs, it was the custom of itinerant craftsmen to spin glass fibers into decorations and ornaments for collectors. However, this material proved to be unsuitable for most purposes, as the tattered, brittle threads could only extend up to ten feet, which was the circle of the largest reels.

     But by the middle of the 1870s, the finest glass fibers were finer than silk, and they could be combined to create faux ostrich feathers that could be used to adorn hats or woven into garments. Spun glass cloth in white had a silvery appearance, whereas fibers extracted from yellow-orange glass had a golden hue. Before their thermal and electrical insulating qualities were recognised and techniques for creating continuous filaments were discovered, glass fibers were essentially a novelty in the 1930s. Glass is supplied directly from a glass-melting furnace into a bushing, a container punctured with hundreds of tiny nozzles, where it emerges in fine streams, as part of the modern manufacturing process. The streams of glass are collected into a single strand and wrapped onto a reel as they solidify.

Which of the following aspects of glass fiber does the passage mainly discuss?