单项选择题

The （）(吊杆托架) supports the derrick.

A. derrick boom rest
B. derrick head
C. derrick mast
D. derrick guy

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单项选择题

A. heavy derrick
B. pulley block
C. topping lift block
D. guy tackle

单项选择题

A. heavy cargo derrick
B. heavy deck
C. jumbo boom
D. heavy block

单项选择题

A. light derrick
B. union purchase
C. topping lift
D. heavy derrick