There have been many great inventions,things that changed th

There have been many great inventions,things that changed the way we live.
There have been many great inventions or things that changed the way we live.The first great invention was the one that is still very important today——the wheel.This made it easier to carry heavy things and to travel long distance.
For hundreds of years after that there were few inventions that as much effect as the wheel .Then in the early 1800s the world started to change.There was little unknown land left in the world.People didn’t have to explore much any more.They began to work instead to make life better.
In the second half of the 19th century many great inventions were made.Among them were the camera,the light and the radio.These all play a big part in our daily life today.
The first part of the 20th century saw more great inventions.The helicopter in 1909,movies with sound in 1926,the computer in 1928,jet planes in 1930.This was also a time when a new material was first made.Nylon came out in 1935.It changed the kind of clothes people wore.
The middle part of the 20th century brought new ways to help people get over diseases.They worked very well.They made people healthier and allowed them to live longer.By the 1960s most people could expect to live to be at least 60.
By this time most people in developed countries had a very good life.Of course new inventions continued to be made.But man now had a desire(渴望) to explore again.The earth was known to man but the stars were not.Man began looking for ways to go into space.Russia made the first step.Then United States took a step.Since then other countries ,including China and Japan,have made their own steps into space.
In 1969 man took his biggest step away from earth.Americans first walked on the moon.This is certainly just a beginning,though.New inventions will some day allow us to do things we have never yet dreamed of.
5.Man didn't have a desire to explore a lot_____.
A.at the beginning of the 1800's
B.from the 1800's to the 1960's
C.in the 1960's
D.since the 1900's请问为什么不是选D?.为什么呢?

答案没错
注意看这段话：
Then in the early 1800s the world started to change.There was little unknown land left in the world.People didn’t have to explore much any more.They began to work instead to make life better.
明显是A,
再问： 我知道啊。。它问的不是人们没有渴望去探索是什么时候吗 从文中看应该是D啊。By this time most people in developed countries had a very good life. Of course new inventions continued to be made. But man now had a desire(渴望) to explore again 在这之间啊。1800s到1960s啊？？？？它其中并不是在探索啊。不是说停止探索去发明东西吗？？ 请问怎么回事？？？