What of these descriptions correctly describe a feature of the Bell$-$La Padula model?

Question $35$ Answer

a$.$

A document$’$s clearance level must be at least the same as a user accessing it$.$

b$.$

A user can access data, provided they are allowed access to a category assigned to the data.

c$.$

A subject can write to documents with a same or lower clearance level.

d$.$

Classification and clearance are decided by users.

e$.$

Enforces confidentiality using user clearance levels together with object categories and classifications.