Sexual reproduction is defined as the process in which male gamete combine with female gamete to form a new organism.
The given example is a type of sexual reproduction as it involves two different sexes a male poplar tree and a female poplar tree, and pollens from male poplar tree transfers to the sex cells on a female poplar tree result in the process of fertilization.
Hence, the correct answer is "Sexual reproduction".
D is the answer because democracy was designed so the people would have a say in what the City State is doing and how they are doing it. It was made so the government would not have leading control. It gave the common people a say.
