Regarding Hofstede's research in IBM from 1967 to 1973, which of the following statements are correct?

A、The questionnaire was designed for cultural research.;
B、Through analysis on the data collected at that time, five cultural dimensions were formed.;
C、Hofstede's cultural theory was built up at the nation level.;
D、Hofstede's cultural theory not only provides new ground for the study of cultural theory, but also is a breakthrough in the research methods of cross-cultural research.