下列关于画面视觉注意力的说法中,正确的有()
A、画面上部比下部强
B、左侧比右侧强
C、侧比左侧强
D、中间比周围边缘强
E、周围边缘比中间强
参考答案:A, B, D
Don't go out to play. You ________ finish your homework first. [ ]
A. must
B. have
C. had
D. had to
硫化氢中毒有何症状?