Since it has the most Red, I'd say the US (d).
Export means shipping goods out of the country. This means that it depends on the country to say what was the export, one country's export in another's import.
For Europe, the export was textiles and rum,
For Africa, it was the slaves,
For America, it was sugar, tobacco and cotton.
Answer: Across subjects multiple-baseline design
Explanation: The single case design involves experiment whereby only one group is used as to make inference in the study, the control group and treatment group aren't distinct. When behavior is measured or observed in two or more participants belonging to a single group by delivering a the same intervention or treatment at different poinf in time. In the scenario above, the smile and eye contact is the treatment being delivered or used on the participants to measure the the level of responsiveness of the participants. After trying the treatment on the first subject, the treatment was so test on the other participants, hence
