军人证件的保管原则？
参考答案：
证件应当随身携带，妥善保管，严禁转借、复制、伪造、涂改，防止遗失和损坏。
—Where is your father?
—He _____ to the Great Wall. He _____ there twice.[ ]
A. went, has been
B. has gone, has been
C. has been, went
D. has gone, went
云、雨、露、霜、雪、雹、雾都是水的“化身”，其中都是固态成分的有______，都是液态成分的有______，有固态、液态等多种成分的是______．
