When a router fails to send messages in a timely fashion, this is a problem of the

transport layer
network layer
data-link layer
application layer

solution:

the right option is a

to adding   a new row to a table we   have to do process last table cell and pressing tab.

this is the process to add new row in the cell:

* to add a row below the cell, click insert below in the rows and columns group.

thus this is the required right answer.