The correct option is
A collateral
'Security' is a group of people responsible for protecting a person, or a building.
Option B - 'Agreement' means to have a same opinion, or a decision that is legally accepted and signed by two or more people, firms or organisations. Thus option B is incorrect.
Option C - 'Assurance' means a promise. Thus option C is incorrect.
Option D - 'Welfare' means help given to the needy by the state or an organisation. 'Welfare' also means physical and mental health and happiness. Thus option D is incorrect.
Option E - 'Prize' means something valuable, or a reward. Thus option E is incorrect.
Option A - 'Collateral' means security for debt, or something pledged as a security for the repayment of a loan. Thus option A is the correct answer.
'Security' - 'Collateral'