In a GIS, a layer is:

A) Like a database table, layers are collections of features of the same type or of the same class.

B) A general-purpose organizational tool that can hold any type of object, much like a directory or folder on a disk drive.

C) One "chapter" of the metadata.

D) None of these.

Features would be represented by a vector model if:

A) The features do not have definite boundaries (they are continuous).

B) If they are directional and so can be readily represented by a mathematical vector (length and direction).

C) The features do have definite boundaries (they are discrete).

D) They do not involve temperature in any sense.