A placebo is kind of a "fake" treatment but, typically the person receiving a placebo is unaware it has no medical effect on them so they believe they are feeling better. For example, a lot of anxiety meds are placebos and people don't know so their brain tricks them into thinking they are feeling less anxious. This could be used in experiments where a group believes they are affected to see how they react
The sun is about 70% hydrogen and 28% helium, so the two elements that make up the Sun almost in its entirety are hydrogen and helium.
<span>The genes that produce the enzymes needed to break down lactose are not expressed.<span> </span></span>