The correct answer is C. Transistor transistor logic.
Transistor transistor logic (TTL) is a type of digital logic that uses bipolar transistors to perform logic functions. It is a relatively simple and inexpensive type of logic, and it was once the most common type of logic used in computers. However, TTL has been largely replaced by CMOS logic, which is more efficient and has a higher integration density.
Switch transistor logic (STL) is a type of digital logic that uses field-effect transistors (FETs) to perform logic functions. It is a more complex and expensive type of logic than TTL, but it has a higher integration density and is more efficient.
Transistor buffer logic (TBL) is a type of digital logic that uses transistors to buffer signals. It is a relatively simple type of logic, and it is often used to isolate different parts of a circuit from each other.
Circuit level logic is a type of digital logic that uses circuits to perform logic functions. It is the most complex type of logic, but it is also the most versatile. It is often used in high-performance applications, such as microprocessors.
In conclusion, C. Transistor transistor logic provides higher integration density.