Never adopt a callous attitude towards your duties.

Answer: Option C

Callous : showing or having an insensitive and cruel disregard for others.
Cooperative : involving mutual assistance in working towards a common goal.
Cautious : (of a person) careful to avoid potential problems or dangers.
Considerate : careful not to inconvenience or harm others.
Courteous : polite, respectful, or considerate in manner.

Antonym of Callous is Considerate