In a parliamentary system, prime ministers can be removed through a vote of no confidence, which is option b.
A vote of no confidence is a parliamentary procedure where members of the legislative body express their lack of confidence in the prime minister or the government. If a majority of the members vote in favor of a no-confidence motion, it indicates that the prime minister has lost the support of the legislature. Consequently, the prime minister may be required to resign, leading to the formation of a new government or the calling of early elections, depending on the specific rules and procedures of the parliamentary system in question.
While elections (option a) play a crucial role in determining the composition of the legislative body and indirectly impacting the prime minister's position, they do not directly remove the prime minister.
Impeachment (option c) typically refers to a process in a presidential system where charges of misconduct are brought against a high-ranking official, such as a president, and a trial is conducted. In a parliamentary system, the removal of a prime minister is generally handled through a vote of no confidence rather than impeachment.
Referendum (option d) is a mechanism by which citizens directly vote on a particular issue or question. It is not a direct method for removing a prime minister in a parliamentary system, as the removal typically rests within the authority of the legislative body rather than being subject to a popular vote.