在核磁共振氢谱中出现两组峰，其氢原子数之比为3：2的化合物（ ）
A．
B．
C．
D．
答案：D
—Here is a nice card.
—Let me ______.[ ]
A. have a look
B. to see
C. have a look at
D. to have a look
决定接头阻力大小的因素有哪些？通常应如何确保必要的接头阻力？
