Questions

Here Homologous Means having the same relation or relative position or structure. 

Here in snakes poison is in glands and here salivary glands are in Vertebrates.

The `fork()’ used to create a new process from an existing process. The new process is called the child process, and the existing process is called the parent. We can tell which is which by checking the return value from `fork()’. The parent gets the child’s pid returned to him, but the child gets 0 returned to him.

C++ is not an Operating System.

An Operating System is a collection of system programs that manages all the other programs application programs in a computer as well as the allocation and use of hardware resources such as the CPU, Memory and the Hard Disk Drive.

It acts as an interface between the hardware and the user level program.

It controls and facilitates the overall operation of a computer. 

Here

UNIX : UNIX is a popular multi-user, multitasking operating system (OS) developed at Bell Labs.

Windows NT : Windows NT is a family of operating systems produced by Microsoft, the first version of which was released in July 1993.

DOS : DOS is Disk Operating System. The term DOS can refer to any operating system.

C++ : C++ is a programming language and computing platform.

Hence, C++ is not an Operating System.