Please choose the correct answer to the question: Spirogyra are green algae that can reproduce sexually. Which of the following features identifies reproduction in Spirogyra as sexual reproduction?

Answer1: The cells of parent algae have nuclei. Answer2: Each offspring contains chloroplasts. Answer3: Several offspring may be produced at once. Answer4: Genetic material is contributed by two parent cells.

Answer format: answer1/answer2/answer3/answer4