Which layer chooses and determines the availability of communicating partners along with the resources necessary to make the connection, coordinates partnering applications, and forms a consensus on procedures for controlling data integrity and error recovery?

 Transport layer

Explanation:  The transport layer of device A establishes a direct link with the transport layer of device B, using the port concept (a logic partition used to identify one application running on the device), exchanging messages in order to set up the communication and using different mechanisms (like sliding window in TCP) in order to recover from errors and controlling data integrity.

which functions return a valid value without any arguments?

(-blank- and -blank- return a valid value without any arguments.)

1st -blank-

today

sqrt

count

2nd -blank-

round

now

sqrt