肛门直肠周围脓肿大多来源于()
参考答案:肛窦感染
对划线部分提问。
1. I go to school by bike.
2. Tom is ten years old.
3. I go to school at 6:30.
4. You can go to the park on foot.
5. Your bag is on the desk.
一元二次方程kx2-2x-1=0有实数根,则k的取值范围是[ ]
A.k≠0且k>-1
B. k≥-1
C. k≠0且k≤-1
D. k≠0或k≥-1