Mammals whose young develop in a pouch on the mother's body are called
placental mammals, monotremes ,marsupials, gymnosperms

The correct answer is: marsupials.

Marsupials are actually defined by their ability to hold the young in the pouches, where they can be well protected. Some examples are Kangaroos and Koalas.

Other answers are wrong: for example, gymnosperms are plants, not animals.

Ithink the dna sequences may vary but the amino acid sequences are identical. 

Sugar + oxygen > carbon  dioxide + water + energy  c6h1206 + 6o2 > 6co2 +6h2o + energy  and the numbers after the element symbols are small.