The term hierarchy refers to
a. a condition in which the weak must die so the strong can survive.
b. a situation in which higher species such as men will always be in control of lower species such as animals.
c. a team in which everyone is equal and has to pull his or her own weight.
d. a power structure in which each member knows his or her own place.

The man of mass m1 and the woman of mass m2 are standing on opposite ends of the platform of mass m0 which moves with negligible friction and is initially at rest with s = 0. the man and woman begin to approach each other. derive an expression for the displacement s of the platform when the two meet in terms of the displacement x1 of the man relative to the platform.

Why is no-till farming more sustainable than many traditional methods of farming

The energy of a photon is equal to (what) times (what) of the photon.