The Graph Here Shows the Results of Jacob and Monod's $\beta$

The graph here shows the results of Jacob and Monod's first experiments with $\beta$ -galactosidase and lactose in E. coli. If $\beta$ -galactosidase were unstable in the absence of lactose (one of the hypotheses they tested) , what results would you expect to see?

A) the results shown in the graph
B) an increase in $\beta$ -galactosidase after lactose is removed
C) a decrease in $\beta$ -galactosidase after lactose is removed
D) an initially high level of $\beta$ -galactosidase at the beginning of the experiment, with a steady decline over time
E) None of the answer options is correct.