Placenta
It also does not allow the maternal and fetal bloodstreams to mix
The correct answers is:
is formed when fuel is burned at high temperatures
<em>Nitrogen dioxide is another toxic gas that forms when fuels are burned at high temperatures.</em>
is the most abundant gas in the atmosphere
<em>The most abundant gas is nitrogen. Over 78 percent of the air we breathe is nitrogen (N)</em>
can cause acid rain
<em>Both nitrogen dioxide and sulfur dioxide can cause acid rain. The damage done by acid rain is devastating to the plants and animals in an ecosystem.</em>
is a major pollutant in the air
<em>AQI measures five major pollutants, including carbon monoxide, nitrogen dioxide (NO2), and sulfur dioxide (SO2).</em>
Wrong answers:
is a waste product of photosynthesis
<em>The waste product of photosynthesis is oxygen.</em>
