The 19th century saw a great change    ⓐ    machines and electricity became common. That was the Indu- strial Revolution. The world ⓑ went through another big change in the 20th century due to the advent of the computer. Now,     ⓒ      the 21st century we are amazed by a new scientific discovery which will cause another great change.    ⓓ   , a  team of scientists has made a map of the DNA in    the human body and the body's secrets ⓔ analyze. But people have a little understanding of this new scientific discovery.