He was noticed ________ basketball on the playground. [ ]
A. played
B. play
C. to play
答案:C
老年人睡眠时,后半夜()。
A、正相睡眠较多
B、异相睡眠较少
C、较熟睡
D、较惊醒
双扩试验平板法中,若抗原抗体含量相同,则反应沉淀线应
A.靠近抗原孔B.靠近抗体孔C.在两孔之间D.呈多条沉淀线E.不出现沉淀线