On the weekends, Eliza only reads romance novels. During the week, Eliza paints three days a week unless she has pressing family obligations or is substitute teaching at the local art school. Four days a week, Eliza practices her cello, and on Wednesdays, she gives cello lessons. Last week, Eliza had no pressing family obligations, nor did she substitute teach at the local art school. Ttherefore, she must have practiced her cello on Monday, Tuesday, Thursday, and Friday. Which one of the following is an assumption on which the argument relies?
A: There was at least one day last week when Eliza read romance novels and painted.
B: Eliza does not practice her cello on the day that she gives cello lessons.
C: Eliza does not give cello lessons on days that she substitute teaches at the local art school.
D: Eliza never has pressing family obligations on the day she gives cello lessons.
Choose A, B, C or D as your solution.
B