伴有眼底视网膜色素变性的遗传性脊髓小脑性共济失调（SCA）亚型是（）
A.SCA1
B.SCA3
C.SCA6
D.SCA7
E.SCA8
参考答案：D
附加题：
A、计算：2-1=______；
B、在正方形、直角三角形、梯形这三个图形中，为中心对称图形的是______．
Don't worry. I _____ you as soon as I finish my work. [ ]
A. help
B. will help
C. helped
D. was helping
