B

Step 1: Understand what a P-type semiconductor is. A P-type semiconductor is formed when a trivalent impurity (having three valence electrons) is added to a semiconductor material (like silicon or germanium). This impurity creates 'holes' in the crystal lattice, allowing it to conduct electricity through these positive charge carriers.
Step 2: Identify the trivalent impurities.
Step 3: Review the given options:

• Option A: As impurity is mixed in Si A and C (This does not specify a trivalent element)
• Option B: Al impurity is mixed in Si A and D (correct, Al is a trivalent element)
• Option C: B impurity is mixed in Ge B and C (B is also trivalent, but the focus is on Si)
• Option D: P impurity is mixed in Ge B and D (this does not create a hole, as P is not a trivalent element).

Conclusion: The best option that describes the formation of P-type semiconductor is Option B.