Final answer:
Grass seed consists of a caryopsis encased between two protective bracts, with the lemma being the outer bract and the palea being the inner bract.
Step-by-step explanation:
Grass seed is composed of a caryopsis sandwiched between lemma (outer bract) and palea (inner bract). So the correct answer is a) Caryopsis; lemma; palea. The caryopsis is the true seed of the grass which is fused with the fruit, the lemma is the outer bract that protects the caryopsis, and the palea is the inner bract, also providing protection and support.