At least one of the second and third lens groups can include a single lens.

第二和第三透镜组中至少一组，可以包括单个透镜。

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Single sand body occurs generally as tabular mass or wide lens.

单砂体多呈板状和宽透镜状。

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Single sand body occurs generally as tabular mass or wide lens.

单砂体多呈板状和宽透镜状。

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