Shellie takes college courses that interest her and enjoys learning for its own sake; Tori takes courses in which she is fairly certain she'll do well and studies mainly to ensure good grades. In psychological terms, Shellie is motivated; Tori is motivated.

intrinsically; extrinsically                                                                            

Explanation:

Intrinsic motivation: In psychology, the term "intrinsic motivation" is described as an individual's behavior that is being driven by different "internal rewards" i.e, a form of motivation in which an individual is being engaged in behaviors that come from within him or her as it was naturally satisfying him or her.

Extrinsic motivation: In psychology, the term "extrinsic motivation" is described as an individual's behavior that is being driven by some external rewards, for example, praise, money, grades, etc and generally comes from outside the person.

the answer might be either a or c. can't be too sure , because i searched the web, but no valid answers came through.

what is the tax base for the sales tax?

it should be (usually ) 6%