Correct Answer  Option 2 : Number of bits per second that can be transmitted over a network
Bit rate is commonly measured in bits per second (bit/s) and often includes a prefix, such as 'kilo', 'mega', 'Giga', or 'Tera'.
 One kilobit per second (kbit/s) is the equivalent of 1000 bits per second.
 In video streaming, bitrate refers to the number of bits that are conveyed or processed in a given unit of time.
 In most computing and digital communication environments, one byte per second (1 B/s) corresponds to 8 bits.
Number of bits stored in a computer 
Number of bits per second that can be transmitted over a network 
Number of bits per hour stored in a computer over a network 
Binary digit converted to hexadecimal number 
The size of information in the computer is measured in kilobytes, megabytes.

The number of bits that are transmitted over a channel or network each second (bits per second, or bps) is called the bit rate (also known as data rate). 
A collection of 8 bits is called a byte and (on the majority of computers today) a collection of 4 bytes, or 32 bits, is called a word. Each individual data value in a data set is usually stored using one or more bytes of memory, but at the lowest level, any data stored on a computer is just a large collection of bits. 
Hexadecimal numerals are widely used by computer system designers and programmers because they provide a humanfriendly representation of binarycoded values. Each hexadecimal digit represents four bits (binary digits), also known as a nibble (or nybble), which is half a byte. 
Hence, we may say that Bit rate is the number of bits per second that can be transmitted over a network.