线是可数名词还是不可数名词

It took me a long time to thread my way through the crowd.

我花了很长时间才从人群中挤过去。

The author skilfully draws together the different threads of the plot.

作者娴熟地把情节的.各种线索串联在一起。

A common thread runs through these discussions.

这些讨论都贯穿着一条共同的主线。

A tiny wire is threaded through a vein to the heart.

一根细金属丝从静脉里穿到心脏。

She snipped at the loose threads hanging down.

她把垂下来的线头剪掉。