问题如下：
Which of the following describes privately placed bonds?
选项：
A. They are non-underwritten and unregistered.
B. They usually have active secondary markets.
C. They are less customized than publicly offered bonds.
解释：
A is correct.
Private placements are typically non-underwritten, unregistered bond offerings that are sold only to a single investor or a small group of investors.
请问A里的non-underwritten怎么理解？不能承销，只能包销吗？
