What terms in the following paragraph help the reader visualize a sequence of events?
“The trouble starts when unusually large amounts of greenhouse gases build up in the atmosphere. Then the heat cranks way up. Human activities—such as the burning of fossil fuels, like coal and petroleum—release billions of tons of greenhouse gases into the atmosphere every year. And deforestation (clearing of forests) removes the trees that would otherwise absorb carbon dioxide.”
a.
starts, then, removes
c.
when, then
b.
begins, after
d.
all of these

Question

What terms in the following paragraph help the reader visualize a sequence of events? 
“The trouble starts when unusually large amounts of greenhouse gases build up in the atmosphere. Then the heat cranks way up. Human activities—such as the burning of fossil fuels, like coal and petroleum—release billions of tons of greenhouse gases into the atmosphere every year. And deforestation (clearing of forests) removes the trees that would otherwise absorb carbon dioxide.”
a.
starts, then, removes
c.
when, then
b.
begins, after
d.
all of these

AP · Answer

Process of elimination -
The terms "starts" and "removes" do not necessarily indicate a sequence of events so option A.) can be eliminated and so you can also remove option D.) 
And this paragraph does not include the words "begins" and "after", so B.) can also be eliminated.
The words "when" and "then" (C) suggest a sequence of events in this paragraph

Good luck (: