单项选择题
What is the reason for using higher pressure (100-1000 Pa which is about 1 Torr to 10 Torr) in the analysis chambers of environmental scanning electron microscopes (ESEM)?
A、To amplify electron signal via electron multiplication
B、To compensate negative charges deposited on samples by electron beams
C、To limit desorption of water in biological samples
D、To provide high contrast images and eliminate conductive coatings at observation of insulating samples
E、All above
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