急性白血病和慢性白血病的主要区别是（）
A.肝脾是否增大
B.起病缓急
C.白细胞剧增程度
D.贫血严重程度
E.骨髓幼稚血细胞成熟程度
参考答案：E
四艺
After people have learned that magnets attract things, centuries passed______they took note of the fact that magnets sometimes also repel things.
A．before
B．until
C．after
D．since
