Call risk pertains to callable bonds and is the risk of the bond issuer "calling the bond" when interest rates decrease. The issuer replaces the current bond with lower interest rate debt but the current bond holder usually loses due to having to replace their bond with a lower paying coupon bond. This has nothing to do with floating rate bonds. The rest of the choices are reasons why floating rate bonds fluctuate from par.

With a cap, when the market yield is above its capped coupon rate, a floating-rate security will trade at a discount.  With fixed rate margins, if the creditworthiness of the firm improves, the floater is less risky and will trade at a premium to par.