A scavenger is someone who searches through waste or discarded items to find and collect useful things. This word fits the meaning given in the question exactly.
Option B, pauper, means a very poor person who has no money. This word has nothing to do with searching for discarded items.
Option C, beggar, is a person who asks others for money or food. Begging is different from collecting discarded items.
Option D, bankrupt, describes a person or company that cannot pay its debts. This word is about financial failure, not about collecting items.
Since only scavenger matches the definition, the correct answer is option A, Scavenger.