Correct

笃

/ dǔ / 
Strokes

Definition

serious (illness)/sincere/true

Example

As an Adjective

sincere; earnest

1
Yǒuyì
友谊
shéndǔ
甚笃

be in devoted friendship

2
Àiqíng
爱情
shéndǔ
甚笃

be in deep love

As an Adjective

(of an illness) serious; critical