[CISSP-D] Two questions about Security Models and Architecture in All-In-One

Hi, everybody,

I read the All In One. The following two questions confused me. would you 
please help me?

Chap.5---22
Which best describes the *-integrity axiom?
A. No wirte up in the Biba model
B. No read down in the Biba model
C. No write down in the Bell-lapadula model
D. No read up in the Bell-lapadula model

The answer is A. Why not C?

Chap.5---23
Which best describes the simple security rule?
A. No wirte up in the Biba model
B. No read down in the Biba model
C. No write down in the Bell-lapadula model
D. No read up in the Bell-lapadula model

The answer is D. Why not B?

The Bell-lapadula has the simple security rule, the *-property rule.
The Biba has two integrity rules.

I think the first one is because of the "integrity". What's the reason for the 
second one? Is there special names for Biba rules? 

Thanks a lot.

Shujing