question: What are atoms of the same element that differ in their numbers of neutrons called?
distractor3: opposites
distractor1: reactions
distractor2: organisms
correct_answer: isotopes
support: The first plants were probably similar to the stoneworts in Figure below . Stoneworts are green algae. Like stoneworts, the first plants were aquatic. They may have had stalks but not stems. They also may have had hair-like structures called rhizoids but not roots. The first plants probably had male and female reproductive organs and needed water to reproduce. In stoneworts, sperm need at least a thin film of moisture to swim to eggs.