The series of valves used to control the return flow in well control operations is called the().
A. valve assembly
B. standpipe manifold
C. accumulator manifold
D. choke manifold
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均衡的国民收入水平取决于()
A. 单纯的商品总供给量
B. 单纯的商品总需求量
C. 总价格水平
D. 总供给量与总需求量相互作用直至相等