I'll give you a question, please answer with step-by-step reasoning process.
What occurs when gametes fuse to form a diploid zygote?\nOptions:\n- (A) permineralization\n- (B) rapid expansion\n- (C) competition\n- (D) fertilization\n- (E) photosynthesis\n- (F) chromosomes\n- (G) mutation\n- (H) Leptospirosis

(D)
Fertilization occurs when a sperm and an egg fuse to form a diploid zygote.

Sperm and eggs are cells known as gametes.

Fertilization occurs when gametes fuse to form a diploid zygote.

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So, the answer is (D)