Ah, test questions got to love them.
A. Reducing the amount of time between log backups will reduce the size that the log grows.
B. You always want the smallest transaction size (I’m assuming that is what you are talking about here) do reduce database locking. Reducing transaction size won’t reduce the size of the transaction log though.
C. Only use the SIMPLE recovery mode if you don’t want point in time restore. As you need to do transaction log backups you can’t use SIMPLE recovery mode.
D. Never ever use DBCC ShrinkFile unless you really, really need to. There is no acceptable reason to schedule DBCC SHRINKFILE to run on a regular basis. All running DBCC SHRINKFILE will do is cause file fragmentation on the physical disks and the VLFs within the log.