粗纤维由（）、（）、（）组成。
参考答案：纤维素；半纤维素；木质素
The split between humans and living apes is thought by some scholars _____ 15 to 20 million years ago. [ ]
A. to occur
B. occurring
C. to have occurred
D. having occurred
下列哪种细菌在25℃培养时是动力阳性，而在37℃培养时是动力阴性？（）
A.小肠结肠炎耶尔森菌
B.痢疾志贺菌
C.弗劳地枸橼酸杆菌
D.鼠伤寒沙门菌
