影响样本规模的因素中，通常不包括（ ）。

多项选择题What are the correct statements about pepsin?（ ）A.The optimum pH is 2.0B.Pepsinogen can be activated by H+C.Pepsinogen can be activated by trypsinD.pepsin is a binding enzymeE.Pepsin

单项选择题按十二经脉的流注顺序，下列正确的是 A．手少阴经-手太阳经-足少阴经 B．手阳明经-足阳明经-足太阴经 C．足少阳经-足厥阴经-手少阴经 D．足太阳经-手厥阴经-手少阳经 E．足少阴经-手厥阴经-足少阳经