A、Canopy-mounted spray systems
B、Shield sprays on the underside of the canopy
C、Air dilution
D、Unidirectional cutting sequence
A、more powerful and faster/cutting speeds exceeding 100 fpm
B、shield movement can be a significant source of dust
C、coal and/or rock fall from the top of the shield canopy directly into the airstream
D、requires shields to advance at a faster rate
From the passage it can be inferred that ______.
A.all school children are offered a course in the use of computer
B.all unemployed workers are being retrained
C.in reality only a certain portion of unemployed workers will be retrained
D.retraining programmes are considered very important by the government
From the passage we can find out that the author mainly studies ______.
A.patterns of family behavior
B.women who are initiating social change in a small region in Texas
C.migrant agricultural workers
D.how migrant farm workers lived in the past
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