目前依然保留了较多原始村落的大洲是[ ]
A.亚洲
B.欧洲
C.北美洲
D.非洲
答案:D
Look, read and judge. 仔细看下面这幅图画,判断下面的描述是(√)否(×)正确。
( ) 1. This is a bedroom.
( ) 2. The picture is above the bed.
( ) 3. The dresser is beside the bed.
( ) 4. The slippers and the teddy bear are under the bed.
( ) 5. The closet is beside the dresser.
( ) 6. The ball is on the bed.
神经纤维动作电位上升相是由于
A.K+外流B.Ca2+内流和K+外流C.Na+内流D.Ca2+缓慢内流E.Na+和Ca2+内流