Gaurd cells is right answer that is option C .
Hope it helps.
<h2> Ecological Footprint</h2>
The ecological footprint is an indicator that accounts for human demand on global biological resources. If a person observed his ecological footprint, there will be less environmental problems like carbon emissions, lack of fresh air, global warming and increased environmental pollution would be reduced.
<h3>Impact of ecological footprint</h3>
One of the four categories of ecological footprint can serve as an environmental indicator because the category causes impact on the environment which leads to change in the environment so we can conclude that the category of ecological footprint can serve as an environmental indicator.
Learn more about environment here: brainly.com/question/17413226
Learn more: brainly.com/question/26166448
I think its the second one.....
A) A flap in the heart located between each atrium and ventricle.
Hope it helps! :)
