Questão 29 — Língua Inglesa: Voz Passiva

Texto-base:
Read the text and answer questions 28, 29 and 30.
The Greenhouse Effect

1 A greenhouse is a house made of glass. The sun shines
right through the glass and makes it warm inside the
greenhouse. It is possible to grow flowers and
vegetables inside a greenhouse in the winter. Scientists
5 have a theory that a lot of carbon dioxide in the
atmosphere will act like the glass in a greenhouse. As
the sun shines through the carbon dioxide blanket, the
atmosphere will get hotter and hotter.
Carbon dioxide is produced by combustion, the burning
10 of fuel. It is being added to the normal atmosphere as
we have more and more cars, more and more houses
and industries. In short, more people produce more
carbon dioxide.
Scientists predict that as a result of more carbon dioxide
15 in the atmosphere, there will be a global warming, or a
long-term rise in temperatures over the earth.
(Adapted from “Time and Space”)

In the sentence “It is being added to the normal atmosphere” (line10), we can find the passive voice of which verb tense?