Hypervisors

Correct Answer: Resource allocation

Among the provided answers, 'Resource allocation' is the best solution to improving the performance of a virtual machine that is running slowly despite having adequate resources. This feature enables the virtual machine to utilize resources effectively and efficiently as it allows for the adjustment of resource limits based on the current needs and demands of the virtual machine, thus optimizing its performance. 'VM autostart' refers to the feature that automatically starts a virtual machine and does not directly impact its performance once it's running. 'Nested virtualization' allows for running a virtual machine within another virtual machine which can, in fact, increase the resource strain. 'Virtual NIC teaming' enhances network traffic but not the overall performance of the VM.

Correct Answer: VMware ESXi

The correct answer is VMware ESXi. It is a type 1 hypervisor which means it runs directly on the hardware. Type 1 hypervisors are also known as bare metal hypervisors because they have direct access to the physical hardware, which results in better performance and efficiency. On the other hand, Oracle VirtualBox, Microsoft Virtual PC, and Parallels Desktop are type 2 hypervisors. They run on a host operating system that provides virtualization services, such as I/O device support and memory management.

Correct Answer: Network-based Intrusion Detection System (NIDS)

The best answer is 'Network-based Intrusion Detection System (NIDS)'. This is because NIDS is a network security feature for monitoring and protecting virtual machines against malware and other potential threats. It works by examining the traffic going in and out of your network, looking for suspicious activity that could indicate a malware attack. When NIDS detects potential danger, it can take predefined actions to protect your virtual machines. On the other hand, a 'Virtual switch' is simply a software program that allows virtual machines to communicate with each other within the same physical host. A 'Pass-through disk' is a physical disk that is directly attached to a virtual machine, bypassing the hypervisor. And 'Fault tolerance' is a feature that allows a system to continue operating properly in the event of the failure of some of its components. While all these features have their own uses in the context of a virtualized environment, they do not specifically provide protection against malware which is what the question is asking for.