设向量α与向量β的夹角θ=π/3,模|α|=1,|β|=2,则模|α+β|等于( )。
A A.<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251114/23827764_0.png"> B
B.<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251114/23827764_0_1.png"> C
C.<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251114/23827764_0_2.png"> D
D.<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251114/23827764_0_3.png">