What is it called when the value of one non-key field is functionally dependent on the value of another non-key field?

Match the following types of files to their description

I. Drive imaging A. Unique digital signature of data II. Drive slack B. Additional sectors created to fill a cluster III. Cyclic redundancy check C. Application that prevents changes to a hard drive IV. Message digest D. Captures a "snapshot" of everything on the drive V. Write blocker E. Mathematical computations that validate a copy

Which of the following is an older VPN protocol based on point-to-point protocol?

a. PPTP b. PPP c. L2TP d. IPSec