益生元
参考答案:
是指不被宿主消化吸收,但能选择性地促进宿主消化道有益微生物,或饲喂的益生菌的活性和生长,从而对宿主有益的饲料或食品中的某些成分,如寡果糖等。
—Why did Sam weep?
—He couldn’t stand _______ like that before the whole class.
A.making fun of
B.being made fun of
C.to be laughed at
D.being made fun
引起机床振动的振源有()振源和()振源。