----- Nội dung dịch tự động từ ảnh -----
Rewrite the text using the passive where possible. Make sure the words
underlined do not appear.
Nobody knows exactly when someone invented gunpowder. People know for a
fact that the Chinese made rockets and fireworks long before people used
gunpowder in Europe, which occurred at about the beginning of the thirteenth
century. We generally believe that gunpowder brought to an end the 'Age of
Chivalry', since anyone with a firearm could bring down a mounted knight. In
fact, people did not develop efficient firearms until the sixteenth century. They
used gunpowder mainly in siege cannon when people first introduced it. Later
they used it in engineering work and in mining, but they found that it was
extremely dangerous. Modern explosives have now replaced gunpowder, but we
still use it for making fireworks, just as the Chinese did.
It is not known exactly...