Final answer:
The time frame before deaf people could use the telephone was approximately 80-90 years, which is not reflected in the given multiple-choice answers. TTY technology enabling telephone communication for the deaf was developed in the 1960s, long after the telephone's invention in 1876.
Step-by-step explanation:
The question regarding how long it was before deaf people could use the telephone does not conform to the reference information provided, which is about the minimum frequency variation required for humans to distinguish two separate sounds. Therefore, we can't directly answer the question with the available reference information. However, looking at the history of telecommunications, it is important to note that the telephone was invented in 1876 by Alexander Graham Bell, and TTY technology (teletypewriter, also known as telecommunications devices for the deaf or TDD) that allowed deaf individuals to use the telephone network was developed by Robert Weitbrecht in the 1960s. So it was approximately 80-90 years after the invention of the telephone that devices facilitating telephone communication for the deaf were created, which suggests that none of the multiple-choice options (A, B, C, or D) are correct.