And just now, we were on the upper layer.

而我们刚才就是在上面。

The upper layer of felt should overlap the lower.

毛毡的上层应与下层重叠。

The upper layer of the serum was determined for blood sugar.

结果随着时间的延长上层血清中血糖值迅速下降。

This is covered by an upper layer of warm air that ACTS like a lid.

上面的暖空气层覆罩着它们，作用就像一个盖子。

The bookcase has three layers. I put the thickest books on the upper layer.

书柜分三层，我把最厚的书放在最上层。