On the basis of energy band theory, semiconductors have an almost _____[1] valence band and an almost _____[2] conduction band and ____[3] forbidden energy gap

• A. [1]full, [2] empty,[3]narrow
• B. [1]empty, [2]full,[3]big
• C. [1]full,[2]full,[3]no
• D. [1]empty,[2]empty,[3]narrow