After gaining wireless access to a private network, the attacker can do the following such as launching external attacks, stealing data and cause harm to internal clients in which it is all seen in the choices above and the only thing that he couldn't do is letter c, conduct a slaac attack. The correct answer would be letter c.
Slaac attack is a way of attacking iPV4 networks with the use of iPV6 in which this couldn't be done as it is rare for this type to be used, making it hard and difficult for them to even do.
