the water of the lake was so ------that it looks like glass?中间是填still还是calm?为什么?

calm
calm主要用于气候、海洋“ 风平浪静的”, 也可指人表示“安静的”、“镇静的”, 如:
The sky is blue, and the sea is calm.
天空碧兰, 海上风平浪静.
Although she was frightened, she answered with a calm voice.
虽然她害怕, 但还是用平静的声音回答.
still 指“没声音的”、“没动静的”, 如:
the still hours before dawn
黎明前的寂静时刻.