What is the main difference between the batch and at commands?

A.
The batch command will run multiple times. The at command will only run once.

B.
The commands of a batch job run sequentially one after another while the commands in at jobs
may run in parallel.

C.
The at command reads commands from standard input. The batch command requires a
command line argument.

D.
The at command e-mails results to the user. The batch command logs results to syslog.

Explanation: