They mimicked the flight of birds.
A Diels-Alder reaction is an addition reaction involving a substituted alkane and a diene forming a cyclic aromatic compound. The resulting cycloalkene will be disubstituted with only one double bond in the ring. The 2 pi bonds from the diene will be replaced by 2 sigma bonds.
The answer is A. Two molecules of potassium chloride react with one molecule of lead nitrate to form two molecules of potassium nitrate and one molecule of lead chloride.
1)The state or phase in which most ionic compounds occur will be a solid state or phase. This will make the correct answer A.
2) The compound Co is an example of a covalent compound. This will make the answer to be D.