But they're designed so that they can test every level from a beginner right through to advanced.

但它们的设计使其可以测试从初学者到高级的每个级别。

He said they should also expect to go through levels of sadness, which include denial, anger and depression.

他说，他们也应该预料到会经历各种程度的悲伤，包括否认、愤怒和抑郁。

The shape of a snow crystal may change from one form to another as the crystal passes through levels of air with different temperatures.

当冰晶穿过不同温度的空气层，可以从一种形状转化成另一种形状。

The kidneys regulate our levels of red blood cells through the release of erythropoietin, a hormone which causes marrow to increase production.

肾脏通过释放促红细胞生成素来调节我们的红细胞水平，促红细胞生成素是一种导致骨髓增加产量的激素。