A ros$2\_\_\_\_\_\_\_\_\_\_\_\_$ is a channel through which information flows.

$2.$ Choose the set of words that complete the gaps. A ros$2------------------------$ is a node that writes information into a $-----------------------------.$

$3.$ A ros$2--------------------$ is a node that receives information on a given topic.

$4.$ You want to see the structure of a ros$2$ message geometry$\_$msgs$/$msg$/$Twist$.$ What is the correct command?

$5.$ What does the command ros$2$ topic echo $/$cmd$\_$vel do$?$