9.What did the researchers do with the collected data?
A.They designed a computer program.
B.They created 3D models of the volcano.
C.They studied some volcanoes systematically.
D.They measured some other ground movements.
10.What does the underlined word "they"in the last paragraph refer to?
A.The researchers.
B.The cameras.
C.The models,
D.The volcanoes.
11.What can be the best title of the text?
A.How drones can monitor explosive volcanoes
B.How drones are used to handle active volcanoes
C.What cameras are used in drones for volcanoes
D.What roles drones play in studying ground movements