Final answer:
The percentage of human resource professionals who responded to the poll cannot be determined from the information provided as we need the number of respondents to calculate the response rate.
Step-by-step explanation:
The provided information does not contain the number of human resource professionals that responded to the poll, thus the correct answer is option 4) Cannot be determined. Without knowing the total number of responses, we cannot calculate the response rate.
To determine a percentage, such as the response rate to a survey, one needs the number of respondents and the population size that was approached initially. If, for example, we knew that 237 out of 520 human resource professionals responded, then we'd calculate the percentage by (237/520)*100%, giving us a response rate. Using the information given across other examples, it's clear that calculating a percentage without complete data is not possible.