Volvox, the green algae illustrated here, is considered a colony. yet some scientists argue that it is more like a multicellular life form. in order for a cell or group of cells to evolve into a multicellular organism, all but one of these events must occur. that is
a cells are bound together
b cells specialize and cooperate
c cells form a protective outer sheath
d cells have like pairs of chromosomes

The correct answer is B- cells specialize and cooperate

Explanation:

A unicellular organism is made up of single-cell and this single cell performs all the function to make the organism live and multicellular organisms are made up of multiple cells that are organized and each cells are specialized for performing a particular function and each cell in a structure cooperated each other to support the organism.

Therefore for a cell or group of cells to evolve in a multicellular organism, the cells must be specialized to perform different functions and should cooperate each other to perform these functions.

Volvox can live in colonies which can have 50,000 cells but they are unicellular because each cell is not specialized to perform different function.

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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a. the production of carbon dioxide through the process of photosynthesis