在北方地区的冬季,下面给出的4个外墙节点构造,哪一个保温效果最好?
A <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251122/21142951_0.png"> B
<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251122/21142951_0_1.png"> C
<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251122/21142951_0_2.png"> D
<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251122/21142951_0_3.png">