So clearly _____ that I was able to understand much of what he said. [ ]

A. did he say

B. he told

C. did he speak

D. he talked

下列说法正确的是

A) 共享数据的所有访问都必须作为临界区
B) 用synchronized保护的共享数据可以是共有的
C) Java中对象加锁不具有可重入性
D) 对象锁不能返还