下列不属于光源的是（ ）
A：太阳
B：月亮
C：萤火虫
D：亮着的电灯
选修4-4：坐标系与参数方程
在直线坐标系xOy中，曲线C1的参数方程为 {x=acosty=1+asint （t为参数，a＞0）．在以坐标原点为极点，x轴正半轴为极轴的极坐标系中，曲线C2：ρ=4cosθ．
根据短文理解选择答案。
FILA Men's T-shirts
Made in: China
Colour: white
Size: M
Material: cotton
Wash them with warm water in machines (洗衣机).
Price: ￥320
FIRS Men's Coats
Colour: grey
Size: L
Material: 98% wool, 2% cotton
Dry cleaning (干洗) only.
Keep them in dry and cool places.
Price: ￥1320
Senda Women's Shoes
Colour: pink
Size: M (235 mm)
Material: leather
Keep away from water.
Price: ￥820
西北地区的地形是（ ）
