下列各组中属于相对性状的是[ ]
A．玉米的黄粒和圆粒
B．家鸡的长腿和毛腿
C．绵羊的白毛和黑毛
D．豌豆的高茎和豆荚的绿色
答案：C
首字母填空。
1. It's r _______ warm today, isn't it?
2. Here's today's w _______ report.
3. The sun r _______ in the east in the morning.
4. What's the d _______ today? It's March 1st.
5. Doctors need m _______ to help sick people.
微分方程y"=ex通解为（）。
A．y＝C1ex+C2x
B．y＝C1ex+C2x2+C3
C．y＝ex+C1x+C2
D．y＝ex+C1x2+C2x+C3
