The correct answer is: B. accustomed.
To be accustomed to something means to be used to it or familiar with it. In this case, the sentence is saying that everyone knows that he is not used to hard work. This could mean that he has never had to work hard before, or that he does not enjoy working hard.
The other options are not as good fits for the sentence. Option A, trained, means to have been taught how to do something. This does not necessarily mean that someone is used to doing something, even if they have been trained to do it. Option C, willing, means to be prepared or eager to do something. This does not necessarily mean that someone is used to doing something, even if they are willing to do it. Option D, suitable, means appropriate or fitting for a particular purpose. This does not necessarily mean that someone is used to doing something, even if they are suitable for doing it. Option E, addicted, means to have a strong and uncontrollable need for something. This does not necessarily mean that someone is used to doing something, even if they are addicted to it.
In conclusion, the correct answer is B. accustomed.