Deterrents are measures taken to discourage or prevent fraudulent activities. They are typically punitive actions that are announced following any act of fraud. The purpose of deterrents is to disincentivize employees from committing fraud by promoting a balance between risk and reward. Examples of deterrents in the context of Anti-Money Laundering (AML) controls include escalation to the relevant financial intelligence unit (FIU), legal pursuits, and closure of accounts. Legal pursuits, in particular, serve as a strong deterrent as they involve the potential for legal action and penalties against those involved in fraudulent activities. This can include fines, imprisonment, and other legal consequences. Therefore, legal pursuits are an appropriate control to include under the 'deterrents' step of AML controls.

Choice A is incorrect. A transaction monitoring system is not a deterrent but rather a detection tool used in the process of Anti-Money Laundering (AML) controls. It helps in identifying suspicious transactions that may indicate money laundering activities, but it does not deter individuals from engaging in such activities.

Choice B is incorrect. Staff information and training are crucial for ensuring that employees understand their roles and responsibilities in preventing money laundering. However, this falls under the 'prevention' step of AML controls rather than 'deterrents'. While well-informed staff can help deter money laundering by being vigilant and proactive, this control itself does not directly act as a deterrent.

Choice C is incorrect. Ethos and values form part of an organization's culture which can influence behavior towards compliance with laws and regulations including those related to AML. However, they do not directly serve as deterrents to money laundering activities.