They help ensure that the changes of the independent variable are affecting the dependent variable
The best and most correct answer among the choices provided by your question is the fourth choice or letter D "<span>The thin membrane that closes the cavity of the middle ear from the outside changes position."
</span>Your ears pop in airplanes<span> because the air high above the surface of Earth is less dense than air near the surface, because air near the surface has all the air above it pushing down. </span>Your inner ear has air trapped in it and as the atmospheric pressure changes, it causes pressure on your ear<span>drum.
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I hope my answer has come to your help. Thank you for posting your question here in Brainly.
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During the process of photosynthesis<span>, plants use energy from the Sun to convert carbon dioxide and water into glucose and oxygen. </span>These products<span> are, in turn, used by the plant or animals that eat the plant during cellular respiration to produce ATP. So it would be Carbon dioxide. Hope this helps. :)</span>
Tracheophyta I think it the first true plant to live on land. Sorry if its wrong.
