C is the answer to this question. Are you familiar with what the ASA 5505 is? This is a type of firewall that comes with all of the features that may be needed for different possible environments? Various networking services can be provided more operationally to ensure that the climate will function properly.
Some people may try to configure their ASA 5505 on their own, especially since there are instructions that are available online. If you want to make sure that it will work properly, you can always hire professionals to do it for you. This way, you can be assured that it will be correctly configured.