The History of Hair Coloring
As far back as 1500 BCE, Egyptians were dyeing their hair with henna —a black dye made from certain kinds of plants. At the time, as in modern society, it was mostly used to cover up gray hairs. Later on, the Greeks and the Romans would make various other dyes in a process that __1__ materials ranging from ynthetic chemicals to crushed leeches. Research revealed that they used lead as a permanent black hair dye. They later found it toxic, __2__, so they turned to leech pastes.
In the 1800s, English chemist William Henry Perkin unintentionally created the first artificial dye. While looking for a cure for malaria, he __3__ created a mauve dye. Another chemist named August Hofmann then isolated color-changing molecules from certain fruit oils, and modern hair dye pigments were born.
Hair dyes continued to develop throughout the 20th century with improved manufacturing techniques and a wider range of colors—even creating new colors like “platinum blonde.” By 1969, dyed hair was so common that hair color ceased to be noted on passports. The fact that it could be changed with ease __4__ it from being a viable distinguishing characteristic.
The global market for hair coloring is anticipated to be worth approximately US$28 billion by 2025, showing a huge __5__ for those products. For many people, a bit of color helps to cover up gray hairs, while others may be simply curious to give being a blonde, brunette, or redhead a try. After all, it's as easy as a trip to the salon—or even to the pharmacy for a o-it-yourself kit.
Ans：1、B 2、D 3、A 4、C 5、B