当胃液pH增加到多少时，胃蛋白酶就失去活性（）.
A.pHl
B.pH2
C.pH3
D.pH4
E.pH5
参考答案：D
4.9548保留整数是______，精确到百分位约是______．
The course _______ for introducing multicultural America ranks first in the list of Popularity Courses among students this term.
A．is intended
B．intended
C．having intended
D．intending
