Which of the following is a couplet?

a) “but the lord seen some sinnin’, and it caused him pain.
he says, ‘stand back, i’m gonna make it rain.'”

b) “to dry one's eyes and laugh at a fall,
and, baffled, get up and begin
so the chace takes up one's life 'that's all.”

c) “i am the grass.
let me work.”

d) “spring morning marvel
lovely nameless little hill
on a sea of mist”

Correct

A.Humans first began planting crops during the Neolithic Revolution. In addition, they also began domesticating animals.

I've underlined the transition words in that sentence -- "in addition."  Words such as in addition, also, or likewise show a relationship of similarity to preceding material in the previous sentence.  Transition words like but, rather, or, and however show a relationship of difference to what was stated in a prior sentence or paragraph. There are also transitional phrases that effects or consequences, like as a result  or in consequence.  There are transitional words/phrases that point to examples or support of a point: for instance, namely, as an illustration, etc.    And there are transition words that set up a conclusion: as has been shown, in summary, etc.