Which of the following statements are true $($as always, in general$)?$ For wrong ticks negative marks are given.

$($a$)$A dag is undirected.

$($b$)$A dag has no cycles.

$($c$)$Every dag has a topological sorting.

$($d$)$An arbitrary graph can be turned into a dag, by orienting the edges appropriately in one of the two possible directions.

$($e$)$If a digraph is not a dag, then it does not have a topological sorting.

$($f$)$A dag is acyclic, and thus has cycles.

$($g$)$A dag is connected.

$($h$)$There are dags with at least one vertex, where every vertex has incoming arcs.