Chapter 12 - Statistics - 12.1 Sampling, Frequency Distributions, and Graphs - Exercise Set 12.1 - Page 777: 16

the class with $35-39$ social interactions

According to the table we have $3$ classes with minimum frequency ($3$): classes with social interactions of $35-39,40-44,45-49$. Out of these the class with $35-39$ social interactions is the class with the lowest amount of social interactions.