The correct answer is A. RTL.
Resistor-transistor logic (RTL) is the first integrated logic family. It was developed in the late 1950s and early 1960s by Bell Labs. RTL uses resistors and transistors to create logic gates. It is a relatively simple technology, but it is not as fast or as efficient as later logic families.
DTL, TTL, and MOS are all later logic families that are faster and more efficient than RTL. DTL stands for diode-transistor logic. It was developed in the early 1960s and is a bit faster than RTL. TTL stands for transistor-transistor logic. It was developed in the mid-1960s and is much faster than RTL. MOS stands for metal-oxide semiconductor. It was developed in the late 1960s and is the fastest and most efficient logic family.
None of the above is not a correct answer.