Correct

不绝如缕

/ bùjué rú lǚ / 
Strokes

Definition

hanging by a thread/very precarious/almost extinct/(of sound) linger on faintly

Example

Definition

(of situation) hanging by a thread; very precarious

1
Tājiā
他家
jī
几
dài
代
dānchuán
单传
  
,
bùjuérúlǚ
不绝如缕
  
。

There has been only one son in his family for generations, making the family/male line precarious.

Definition

(of sound or voice) lingering on faintly

2
Tāmen
他们
de
的
gēshēng
歌声
bùjuérúlǚ
不绝如缕
  
,
huídàng
回荡
zài
在
shāngǔ
山谷
zhōng
中
  
。

Their singing lingered on faintly in the valley.