The answer is firewall. It is a network security device that observes inbound and outbound network traffic and chooses whether to allow or block specific traffic based on a well-defined set of security rules. Firewalls have been a first line of protection in network security for over 25 years. The firewall present a barrier between measured and secured internal networks that can be trusted and untrusted outside networks, for example the Internet. A firewall can be software, hardware, or even both.
the first row in a table is classed as the header row.
and with the last one I'm not sure because as far as I know there's not considered a last row.
Answer:
uses third party CAs to validate a user's identity
Explanation:
The Digital Certificate is the only means that technically and legally guarantees the identity of a person on the Internet. This is an essential requirement for institutions to offer secure services over the Internet. Further:
The digital certificate allows the electronic signature of documents The recipient of a signed document can be sure that it is the original and has not been tampered with and the author of the electronic signature cannot deny the authorship of this signature.
The digital certificate allows encryption of communications. Only the recipient of the information will be able to access its content.
Answer:
A and C
Explanation:
Option A:
In IPv6 there is a rule to reduce an IPv6 address when there are two or more consecutive segments of zeros just one time. This rule says that you can change the consecutive zeros for “::”
Here is an example
How to reduce the following IPv6 address?
ff02:0000:0000:0000:0000:0000:0000:d500
Ans: ff02::d500
Example 2:
2001:ed02:0000:0000:cf14:0000:0000:de95
Incorrect Answer -> 2001:ed02::cf14::de95
Since the rule says that you can apply “::” just one time, you need to do it for a per of zero segments, so the correct answer is:
Correct Answer -> 2001:ed02::cf14:0:0:de95
Or
2001:ed02:0:0:cf14::de95
Option C:
Since in IPv6 there are 
available addresses which means 340.282.366.920.938.463.463.374.607.431.768.211.456 (too many addresses), there is no need of NAT solution, so each device can have its own IP address by the same interface to have access through the internet if needed. If not, you can block the access through internet by the firewall.
