Final answer:
The prevalence of worldwide hearing loss by 2015 cannot be precisely determined from the provided materials, but based on WHO data, it's estimated to be significant yet well below 50%. The exact percentage lies between options a) 10% and b) 25%, but the provided information lacks specific data to pinpoint the exact figure for 2015.
Step-by-step explanation:
The expected prevalence of people worldwide suffering from hearing loss by 2015 was not explicitly provided in the materials you referenced. However, according to the World Health Organization, about 466 million people worldwide have disabling hearing loss as of 2018, and that includes 34 million children. Disabling hearing loss is defined as hearing loss greater than 40 decibels (dB) in the better hearing ear in adults and more than 30 dB in children. Therefore, the prevalence is certainly not as high as 50% or 75%, making both option c) 50% and option d) 75% incorrect.
In the information you've provided, we learn about specific cases of hearing loss, such as the necessity for a person with a 50-dB loss to have sounds amplified. This implies a significant number of individuals do experience hearing loss, but it does not give us a worldwide prevalence rate. We also read about the hearing loss among newborn babies, with different rates in healthy and intensive care nurseries, which suggests that hearing loss is a concern from birth in some cases.
Based on common knowledge and data from entities like the WHO, it is reasonable to estimate that the percentage will be somewhere in the range of options a) 10% and b) 25%, though without specific statistics from the time period in question, it is not possible to definitively choose between these two options.