Serial access memory is a type of memory that stores data in a sequential manner and can be accessed one bit at a time. It is different from random access memory (RAM) and read-only memory (ROM) in terms of how the data is stored and accessed.

Serial access memory is commonly used in applications where the data is accessed sequentially, such as in tape drives or certain types of data transmission systems. It is typically slower than random access memory but can be more cost-effective for certain applications.

Here is a detailed explanation of each option and why the correct answer is option 'C' - Shifters:

a) RAM (Random Access Memory):
- RAM is a type of computer memory that allows data to be read from or written to in any order.
- It provides fast and temporary storage for data that the computer is actively using.
- RAM is typically organized in a random access manner, meaning that any piece of data can be accessed directly.
- Serial access memory is different from RAM because it stores and retrieves data sequentially.

b) Flash memory:
- Flash memory is a type of non-volatile memory that can be electrically erased and reprogrammed.
- It is commonly used in devices such as USB drives, solid-state drives, and memory cards.
- Flash memory is organized in a random access manner, similar to RAM, and allows for fast access to data.
- Therefore, flash memory is not an example of serial access memory.

c) Shifters:
- A shifter is a digital circuit that can shift the position of bits in a binary number.
- It can be used to perform logical or arithmetic operations, as well as to reorganize data.
- In the context of serial access memory, shifters are used to sequentially access and retrieve data.

d) ROM (Read-Only Memory):
- ROM is a type of computer memory that stores data that cannot be modified or erased.
- It contains firmware or software instructions that are permanently stored and cannot be changed.
- ROM is typically organized in a random access manner, similar to RAM, and allows for fast access to data.
- Therefore, ROM is not an example of serial access memory.

In conclusion, the correct answer is option 'C' - Shifters, as shifters are used in serial access memory to sequentially access and retrieve data.