$3.(20$ pts$)$ Choose the most appropriate answer in each of the following cases $($with a brief justification$).$

C: In the basic model of Internet, the available bandwidth Bav along an Internet path L is not known to the end$-$user applications because:

$($i$)$ An application does not know its exact bandwidth demand Bdem when sending data over L;

$($ii$)$ Information about raw path capacity C$($L$)$ is hidden in the Internet architecture layers;

$($iii$)$ Some bandwidth Bc is consumed by an uncontrolled cross$-$traffic flowing over L;

$($iv$)$ Internet provides only a $$best$-$effort$$ model of data transfer guarantees to applications.