A $\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_$ is a class of computer used by people on the move to run personal productivity software, access the Internet, read and prepare email and instant messages, play games, listen to music, access corporate applications and databases, and enter data at the point of contact.

a$.$ single$-$user nonportable computer

b$.$ single$-$user portable computer

c$.$ multiple$-$user computer

d$.$ notebook computer