Why does vladek believe one must eat everything on one's plate?

Because he believes it is displaying proper manners when eating.

Eating everything given to you is a sign of kindness, showing that you thank the cook for preparing and cooking the food.

If this is incorrect, please, don't refrain to tell me. Thank you.

did you figure it out? i need on this same question

the correct answer is b. so you can tailor your resumé to the position.

it is important before sending your resumé for you could add some extra information relating to former jobs that might you get a higher possibility to be hired.

may be the company is looking for an experienced person, and showing you have worked in the area they are looking a person for may give you more positive points!