A registered representative executes trades in a customer's non-discretionary account without obtaining the customer's prior approval. This is an example of:

Why B — Unauthorized trading

In a non-discretionary account, the representative must obtain the customer's permission before executing each trade. Trading without prior authorization is unauthorized trading, which is a serious violation of FINRA rules and can result in fines, suspension, or bar from the industry. Even if the trade is profitable for the customer, it is still unauthorized and a violation. Only in discretionary accounts (with written authorization) can the rep make trading decisions without prior approval for each trade.