The first telephone was invented and patented by Alexander Graham Bell in ________.

Which of the following IPSec modes encrypts the data in each packet but leaves the header unencrypted?

a. Transport b. Tunnel c. Network d. All the above

?If _________ detects an error in the Cascading Style Sheets (CSS) code, a warning such as "Sorry! We found the following error(s)!" appears in the header bar.

Fill in the blank(s) with the appropriate word(s).