A crate is pushed across a frictional surface by a large worker. What is the reaction force (Newton's 3rd Law) to the action force that the worker exerts on the crate.

atomic = no of protons.

mass number-atomic number = neutron number

cell differentiation  is how generic embryonic  cells  become specialized  cells. this occurs  through a process called gene expression. gene expression is the specific combination of genes that are turned on or off (expressed or repressed), and this is what dictates how a  cell  functions.

explanation:

real, smaller and upside-down.   so the answer should be b.