(a) That's wrong. A's advertisement seems to contain all the information necessary for a workable transaction. The CDs are identified and the price stated. But even so, courts are unlikely to consider an advertisement of this type as an 'offer'. This is because the courts tend to presume, as a matter of policy, that advertisements are not intended to signal a readiness to be bound. Advertisements are more likely to be construed as an invitation, asking potential customers to make an offer to buy (an 'invitation to treat'). The same is true of displays of goods in shops.
In exceptional cases the presumption may be overturned. The question to ask is whether the advertisement indicates a readiness to be bound by the stated terms without any express or implied reservation.