Which of the following passages does not include an appropriate transition between two sentences?

a. thousands of years ago, humans started farming for the first time. as a result, human societies grew larger than ever before.

b. humans first began planting crops during the neolithic revolution. in addition, they also began domesticating animals.

c. neolithic humans domesticated animals to themselves survive. for example, domesticated cows provided them with milk to drink.

d. the neolithic revolution was an extremely important event. the neolithic revolution happened thousands of years ago.