In sexual reproduction, the sex cells of two different parents fuse to form:

• A. a zygote
• B. a gamete
• C. an embryo sac
• D. a spore

Answer: (A)

Verified step by step guidance

1. Understand the process of sexual reproduction: In sexual reproduction, two specialized cells called gametes (sperm and egg) from two different parents combine during fertilization.
2. Recall the definition of a zygote: A zygote is the single cell formed immediately after the fusion of the male and female gametes during fertilization.
3. Differentiate between the terms: A gamete is a sex cell (sperm or egg), an embryo sac is a structure in plants that contains the egg cell, and a spore is a reproductive cell used in asexual reproduction, not sexual reproduction.
4. Identify the correct sequence: In sexual reproduction, gametes fuse to form a zygote, which then undergoes cell division and development to eventually form an embryo.
5. Conclude that the correct answer is 'zygote,' as it is the immediate product of the fusion of gametes in sexual reproduction.