Answer: compact, spongy
Step-by-step explanation:
Flat bones have surfaces composed of (compact) bone with internally placed (spongy) bone.
Flat bones are typically thin, although they're often curved. Some examples of flat bones are the cranial in the skull, scapulae which is known as the shoulder blades, ribs, and sternum. They're an attachment for muscles and are used in the protection of internal organs.