当x→0时,asin^2x与为等价无穷小量,则常数a等于( )。
A 3 B
<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/21572475_0_1.png"> C
<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/21572475_0_2.png"> D
<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/21572475_0_3.png">