Select the most appropriate ANTONYM of the underlined word:

Senior executives with years of experience have valuable advice for junior employees - but their decades-younger colleagues also have lots to teach their higher-ups.

Valuable means something of value. 

Option A: Invaluable means something too important to have a value or something indispensable. 

Option B: Priceless, similarly, means something beyond being priced. 

OptionD: Wothwhile means something that is worth the effort it takes. 

All of these options take a positive aspect on the value of the thing. The antonym of valuable would be something that is not valuable. 

Optoin C: Worthless means something which is not worth or have no real use or value. 

Therefore, Option C is the correct answer.