如图为细胞结构图，请据图回答：
如图所示，将长为 1m 的细线上端固定在高度为6m 的悬点处，下端吊一个质 量为 1kg 的小球，细线承受的最大拉力为19N．现将小球拉起一定高度后放开，小球到悬点 正下方时细线刚好被拉断，g=10m/s2．求：
根据短文，选择正确答案。
Van and Ted are twin brothers. They look the same. They are English. They are eleven. They are in No.15 Middle School. They are new students in Class One, Grade One. Van sits in Row One. Ted sits in Row Three.
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