Which type of malware is specifically designed to take control of a user's computer to perform malicious tasks?

The correct choice is Trojan. Trojans are a type of malware that masquerade as legitimate software or files to deceive users into installing them. Once a Trojan is on a system, it may allow unauthorized access to the user’s computer, enabling attackers to perform various malicious tasks, such as stealing data, installing additional malware, or controlling the device remotely.

Trojans are distinct from other types of malware because they do not replicate themselves like worms and are not designed specifically for spying or analyzing user behavior as spyware does. Additionally, while bots can take control of a computer as part of a botnet, they are often installed as a consequence of other types of malware, including Trojans. Thus, the primary function of a Trojan is to gain control over a system by tricking users into enabling access, making it uniquely positioned for the malicious purpose described in the question.