A Researcher Wanted to Examine Whether People Remembered Information Better

A researcher wanted to examine whether people remembered information better with auditory cues or with visual cues. Ten participants were randomly assigned to each of the two groups: one group heard a list of words from headphones, and the other group saw the same list of words from a screen. The participants were then asked to write down as many words as they could remember. The dependent variable was the number of words remembered.
-Suppose out of budget concerns, the researcher included only five participants in each group, tested each participant twice, and used each time as separate observations. It seems likely that

A) the assumption of independence was violated.
B) the assumption of homogeneity of variance was violated.
C) the assumption of independence of covariate and treatment was violated.
D) the assumption of homogeneity of slopes was violated.
E) there is no indication of assumption violation.