The diagram shows a helium atom
name part A

How does pregnancy begin? a) a placenta forms in the uterus b) a sperm reaches an egg in the fallopian tubec) the blastocyst differentiates into two cell types d) contractions begin in the uterine wallapex

What substance is the most acidic. lemon juice. tomato juice. sodium hydroxide. water

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