Since $1975,$ U$.$S$.$ nonfinancial corporations have tended to have debt$-$equity ratios that are:

a$)$ less than $1\mathrm{.}0.$

b$)$ averaging in the $\mathrm{.}8$ to $\mathrm{.}9$ range.

c$)$ steadily rising due to the low interest rate environment.

d$)$ relatively unaffected by stock market movements.

e$)$ relatively stable over time.