新发现的畜禽遗传资源在国家畜禽遗传资源委员会鉴定前，不得与境外机构、个人合作研究利用。
参考答案：对
The world's population has grown to more than six times _____ it was in 1800. [ ]
A. which
B. that
C. what
D. the number
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