颅内压增高患者吸氧叙述不正确的是（）

A.降低PaCO₂使脑血管舒张，脑血容量增多

B.降低颅内压

C.降低PaCO₂使脑血管收缩，脑血容量减少

D.减少脑血流量

E.增加PaO₂

A derivative is most accurately defined as a financial instrument that provides:()

A. an adjustment to another asset’s level of risk.

B. a return based on the return of an underlying asset.

C. an agreement between two parties to provide something for each other.