Saundra says that whenever she drinks coffee in the evenings it interferes with her ability to fall asleep. the more coffee she drinks before sleeping, the less sleep she gets. in the context of correlational research, saundra is describing a between caffeine intake and sleep.

Saundra is describing a "negative correlation" between caffeine intake and sleep.

A negative correlation implies that there is a backwards connection between two factors - when one variable decreases, alternate increments. The other way around is a negative connection as well, in which one variable increments and alternate declines. These correlations are considered in statistics as a method for deciding the connection between two variables.  

Negative correlation.

it would be d). more resources must be obtained to attain that combination of goods and services