a. In general, no—because cross-cultural questions are usually left to cultural psychologists and anthropologists.
b. In general, no—because there are almost no cross-cultural differences in basic social psychological phenomena.
c. Somewhat—most social psychologists are cautious about generalizing their findings to different cultures, but the majority of research is still done only in the U.S.
d. In general, yes—most social psychologists are cautious about generalizing their findings to different cultures, and the majority of research is now replicated in at least one other culture before it is ever published.