How did increasing sanitary practices help the human population grow so high?

Which statement describes characteristics of planarians? a they live in oceans, are parasites, and reproduce only sexually. b they live in fresh water, are parasites, and reproduce only asexually. c they live in oceans, are free living, and reproduce sexually and asexually. d they live in fresh water, are free living, and reproduce sexually and asexually.

Modern sea star larvae resemble some primitive vertebrate larvae. this similarity may suggest that primitive vertebrates

What are the three different shapes, or structures, of carbon-based molecules