Resposta :
The modal verb in this sentence is "Should" means "Deveria".
"Should" indicates advice.
In the sentence, you're advising the person you're talking to to smell the roses.
But, as there is not an "ADVICE" or "CONSELHO/SUGESTÃO" alternative, I see no options unless "OBRIGAÇÃO". It's not correct, but it's the "less wrong".
So, correct alternative:
C) OBRIGAÇÃO.
Enjoy your studies.