A private equity firm is acquiring a technology company through a leveraged buyout $($LBO$).$ To finance the deal, the company issues high yield bonds with a $7\%$ coupon and a $10-$year maturity. The bonds offer five years of call protection and are callable at $104\mathrm{.}5\%$ of par at the end of the fifth year, with a declining call premium thereafter. Which of the following statements accurately describes the bond$$s call protection features?

a$,$ The bond's call protection prevents the issuer from calling the bonds at any time, ensuring a long$-$term financing arrangement until maturity.

b$,$ The declining call premium ensures the issuer pays a constant percentage premium when redeeming the bonds early, which incentivizes holding the bonds until maturity.

c$,$ The bond's call protection increases the issuer's financial flexibility by allowing for early redemption at any time, with a variable premium.

d$,$ The bond's call protection limits the portfolio company's ability to redeem the bonds early, ensuring that the bondholders receive regular coupon payments for the first five years.