Answer: B. Trading instructions can be accepted only from the daughter
Step-by-step explanation:
The customer has been declared legally incompetent which means that he should not be making decisions that have to do with something as serious as trading instructions as he will not be able to comprehend them.
The only person that should therefore take over such roles would be his daughter who is a legal guardian. As she is not his guardian, she is able to take such decisions for him and so the trading instructions should be accepted only from the daughter.