Final answer:
A presidential democracy and a parliamentary democracy are similar in having legislative branches, but differ in the separation of powers: the presidential system features an independently elected president while the parliamentary system's prime minister is selected by the legislature.
Step-by-step explanation:
One way in which a presidential democracy and a parliamentary democracy are similar is that both have a legislative branch that is involved in making laws. A key difference, however, lies in the separation of powers and how the head of government and state are selected. In a presidential democracy, there is a distinct separation of powers where the president is elected independently of the legislature and serves as both head of state and government. Conversely, in a parliamentary democracy, there is an interdependence between the executive and legislative branches, as the prime minister is typically selected by the legislature and can be a member of it.
Additionally, the head of state in a parliamentary system can be a different person, often a monarch or a ceremonial president. Therefore, correct answer to the student's question is: None of the given options (A, B, C, D) are accurate representations of the similarities and differences between the two systems.