Questions

The rule followed here is

7 + 3 - 4 = 6

Similarly,

4 + 2 - 2 = 4

9 + 5 - 4 = 10

Hence, the missing numbers are 4 & 10.

Varanasi and Patna are located on the river Ganga. Lucknow is on the river Gomati. Kanpur and Hardwar too are on the river Ganga. Delhi is another city located on the bank of Yamuna.

While the western Ghats stretch uninterrupted , the Eastern Ghats do not have a structural unity.

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.