血细胞比容是指血细胞（ ）

A．占全血容积的百分比

B．占全血质量的百分比

C．与血清容积之比

D．与血管容积之比

E．与血浆容积之比

An American option is more valuable than a European option on the same dividend paying stock with the same terms because the:()

A. European option contract is not adjusted for stock splits and stock dividends and does not conform to the Black-Scholes model and is often mispriced. 

B. American option can be exercised from date of purchase until expiration, but the European option can be exercised only at expiration. 

C. American options are traded on U. S. exchanges, which offer much more volume and liquidity.