Creating separate VLANs for the accounting and marketing departments is the correct solution to establish distinct broadcast domains. This allows for segmenting the network based on different departments, which not only limits broadcasts to specific areas within the network but also improves overall security by controlling inter-department communication flows. Using ACLs on switches or subnets would not inherently create separate broadcast domains as they do not segment the network at Layer 2, and doing nothing would not improve separation or network performance.