DDR SDRAM只能在时间周期的上升沿传送数据。
参考答案：错
I _____ go shopping when the telephone rang.[ ]
A. was about to
B. was just to
C. had to
D. wanted to
流感病毒的血凝素和神经氨酸酶是（）
A.核酸
B.衣壳
C.包膜
D.壳粒
E.包膜子粒
