Answer : 1. "cache memory"
Explanation :

Cache memory has the least access time among the options provided. Cache memory is a high-speed type of volatile computer memory that provides high-speed data storage and access to the processor. It is faster than main memory (RAM) because it is located on the CPU chip or very close to it and stores frequently accessed data and instructions. Accessing data from cache memory is much quicker compared to accessing it from RAM, making cache memory the fastest type of memory in terms of access time.