You are setting up an application server on a Solaris 9 system. This application will be configured using the user app. This user does not require shell access to the system.

What is the most secure way to add a user?

A.
useradd -d /export/home/app -m app

B.
useradd -d /export/home/app -m -s /bin/csh app

C.
useradd -d /export/home/app -m -s /bin/false app

D.
useradd -d /export/home/app -m -k /etc/skel -s /bin/csh app