Why does conjugation have an Hfr strain and an F-strain not result in two Hfr strains

Which mantle is under the crust the upper mantle or the lower mantle i think it's upper let me know if i'm right

What is the answer for the complicated molecules that make up living things usually contain carbon. why is carbon so important in these molecules?

Amale bird-of-paradise uses a dance to attract mates in which it flaps its tail feathers on the ground and jumps around a potential female mate. a different male bird-of-paradise does a similar dance but it jumps around the female in the opposite direction. the female bird is only attracted to one style of dance, in one direction.