The most appropriate response to why hydras would avoid reproducing asexually when conditions are difficult is: The lack of genetic diversity could mean that all of the hydras die, depending on the situation.
In challenging environments, a population that reproduces only asexually can become highly uniform genetically, making them more susceptible to diseases, predation, and environmental changes. Sexual reproduction introduces genetic diversity, which can enhance the population's ability to adapt to varying conditions and improve overall resilience.