A is a document or physical object which was written
or created during the time under study.
Real Source
Secondary Source
Primary Source
O Fake News

answer; how people relate to each other and influence each other;

answerclassical conditioning;

i think it's d because a "rythem" is a

1)a particular type of pattern formed by rhythm.

2)a strong, regular, repeated pattern of movement or sound.

3) the systematic arrangement of musical sounds, principally according to duration and periodic stress.

so, d mabye.