In the given question, the word ‘ triumphant ’ refers to commodity or someone joyous and proud especially because of triumph or success. 
Complete answer 
Let us dissect the options given to us in this question 
1) Option( A),' spooked', refers to someone made hysterical ; frighted. 
For illustration- She was spooked of the snake. 
2) Option( B), ‘ disturbing', refers to commodity or someone causing torture or solicitude or anxiety. 
For illustration- The videotape I just saw was veritably disturbing. 
3) Option( C), ‘ caliginous', refers to commodity or someone filled with melancholy and despondency; sad. 
For illustration- The rainfall seems veritably caliginous moment. 
4) Option( D), ‘ quiet', refers to commodity or someone characterized by an absence or near absence of agitation or exertion. 
For illustration- Everyone suddenly turned veritably quiet. 
thus, option( C) is the correct answer.