Are attributes of an access structure visible or guessable in a CP-ABE ciphertext? Suppose that Alice has attributes A, B and C. I have a ciphertext with this policy: A AND C. 

Can an adversary guess the attributes and then decrypt the ciphertext? What is the probability of guessing attributes in a ciphertext policy attribute based encryption?
In CP-ABE, the policy (i.e. which attributes are required to decrypt) is usually public. So Alice knows whether her A, B, C satisfy the policy or not. If not, Alice knows for example, D and E are required, but she does not have. She does not need to guess. She cannot decrypt the ciphertext however, because she does not have the private key corresponding to the missing attributes. The private keys are issued by a trusted party who will only issue to keys after verifying the requesting party does possess the attributes.