I very much Disagree. The esophagus runs from your mouth to your stomach.
Our main source of energy is the sun. True.
I don't know what the options were but a material that is very likely going to be challenging to recognize under a microscope as a mixture is a homogeneous mixture. A homogenous mixture is uniform and thus hard to recognize as a mixture. An example is water!
The answer is 1. CO. A gram-molecular mass is defined as mass in grams numerically equal to the molecular weight of a substance or the sum of all the atomic masses in its molecular formula. Since CO2 and CO has both carbon and oxygen, the gram-molecular mass does not change. For a compound with carbon and oxygen, the molecular mass comes respectively from 12 (atomic mass of carbon) + (2 × 16) (atomic mass of oxygen), which is 44 g.
