Which of the following materials do cone bearing plants produce for reproduction? a. flowers b. egg and sperm cells c. anther and stigma d. spores and pollen

Ialready know the answers to these questions and they are on the attachment. but i just need to know why that answer is the correct one. plz asap! this is for a report that i need to email by 10!

[34 points awarded to the best answer, use facts and/or data] 1.) what's the likelihood of thunderstorms occurring in the state of maryland? {this question is for a project for science, use facts and/or data and explain why . 34 points to the best answer]

During crossing-over, a. genetic material is exchanged between nonsister chromatids, resulting in new combinations of alleles. b. nonsister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. c. one homologous chromosome of a tetrad is exchanged with another tetrad, resulting in new combinations of alleles. d. sister chromatids from each homologous chromosome of a tetrad are exchanged, resulting in new combinations of alleles. e. genetic material is exchanged between sister chromatids, resulting in new combinations of alleles.