Pl help it’s for a grade

Which traits do human embryos have that link them to a common ancestor with fish and reptiles? a. scales and tail b. gill slits and scales c. tail and gill slits d. hair and tail

What’s the scientific notation for the number 6,840,000,000

Which statement correctly describes potassium iodide, ki? there is a one-to-one ratio of potassium ions to iodide ions. potassium gains electrons and iodine loses electrons during the reaction. the lattice is held together by potassium anions and iodide cations.