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Burglar must firmly grasp the knowledge necessary to maintain a certain of vigilance.
防盗知识也要牢牢掌握，要保持一定的警惕性。
youdao
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These children need not deliberately to memory, can firmly grasp.
这些知识孩子不用刻意地去记忆，就能牢固地掌握。
youdao
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These children need not deliberately to memory, can firmly grasp.
这些知识孩子不用刻意地去记忆，就能牢固地掌握。
youdao