Homologous organs are

Read the following statements:
Statement $I$: All vertebrates develop a row of vestigial gill slits during the embryonic stage.
Statement $II$: Embryos always pass through the adult stages of other animals.
Which of the following options is correct with reference to these statements?

The evidence for the origin of birds from reptiles is the presence in them of

What does the evolution of the heart from a two-chambered to a three-chambered and finally a four-chambered structure demonstrate?

The banding pattern of chromosomes $3$ and $6$ in humans and chimpanzees indicates that they had a ...... .

Which of the following is a vestigial organ in a python?