The vast jungles of the Amazon rainforest are home to tribes (部落) mostly isolated from the outside world, whose way of life, largely unchanged for hundreds of years, is now increasingly threatened by modern civilization.
Now, scientists discover they can monitor these “uncontacted tribes” using satellites, which would allow inexpensive and safe tracking of these tribes in order to protect them from outside threats.
In order to help preserve these uncontacted Indians, researchers need accurate estimates of their populations. One way to collect this data involves flying over their villages, but such over-flights are both expensive and could fill these native peoples with fear. Another strategy involves meeting individuals on the ground, but among other risks, scientists could accidentally spread disease to members of the tribes.
Instead, scientists investigated whether satellite images could monitor uncontacted tribes. The result was inspiring. They confirmed their locations and measured the sizes of their village, houses and gardens. “We can find isolated villages with remote sensing and study them over time.” Walker told Live Science. “We can ask: Are they growing? Do they move?”
Surprisingly, based on the sizes of the houses and villages, the scientists find the population densities of these isolated villages are about 10 times greater, on average, than other villages of native Brazilian peoples. This may be due to the fact that they have to live closer together because they are not as good at clearing the forest, since they lack modern devices like chainsaws and tractors, the researchers said. The tribes may also be afraid of spreading out due to fear of being attacked by outsiders, Walker said.
The researchers now plan to focus on 29 more isolated villages to “look at their ecology— that is, distance from rivers and roads—and use this to model where else we can find more isolated villages,” Walker said.
Scientists don’t want to meet the Indians on the ground due to the fear that ______.

A．they can’t get accurate data

B．they could pass disease to the Indians

C．they will be attacked by the Indians

D．they will catch disease from the Indians

According to the passage, which of the following about the Indian tribes is NOT true?

A．They lack modern tools to cut forests.

B．Their life styles remain unchanged.

C．They live closer together for defense.

D．They are contacting the outside world.

What can we learn from the last paragraph?

A．More isolated tribes are yet to be discovered.

B．Scientists are able to find 29 Amazon tribes in total.

C．It’s easy for scientists to find isolated villages.

D．More roads should be built for the tribes.

Which of the following might be the best title for the passage?

A．The Disappearing of the Ancient Amazon Tribes.

B．Discovery of Indian Tribes in Remote Mountains.

C．The Threatening of Modern Civilization to Tribes.

D．Research of Isolated Tribes with Modern Devices.