A distribution has mean 100 and standard deviation 15. According to the empirical rule, approximately what percent of values fall between…

The empirical rule says that for a roughly bell-shaped distribution, about $68\%$ of values lie within $1$ standard deviation of the mean, $95\%$ within $2$, and $99.7\%$ within $3$. Here $100-15=85$ and $100+15=115$, so the interval is exactly one standard deviation on each side, which holds about $68\%$ of values, choice B. Choice C ($95\%$) would correspond to $70$ through $130$. Choice D ($99.7\%$) would correspond to $55$ through $145$. Choice A ($50\%$) is not an empirical-rule percentage.