Slow reproduction process is a disadvantage of sexual reproduction. So option A is correct.
Sexual reproduction is much slower than asexual form of reproduction and the meiosis process is much longer and complex than mitosis. The process of sexual reproduction depends on the fertilization and zygote formation which are time consuming processes. This longer duration of reproduction process leads to lesser number of individuals in the population. In this case there may be instances of producing only one organism per year and if by chance no offspring is produced for certain number of years can lead to extinction of the species.
