Discrete Math/Graph Theory/Directed Acyclic Graph

Clear and concise answer please. Thank you

Prove or disprove each of these statements about DAGs: If a directed graph has a source, then it is a DAG If a directed graph has a topological ordering, then it is a DAG. For two distinct vertices nu, v in a DAG, if there exists a path from u to v, then there cannot exist a path from v to u. The number of layers in a DAG G is the same as the number of vertices in the longest path in G. In a DAG G where s is a source, there is a path from s to each other vertex v in G. Given a DAG G, for every vertex v in G, there is a path from v to some sink in G