The elements that fill the d orbitals on the periodic table are called transition metals.
Draw the Lewis dot structure for each atom of the compound to show how many valence electrons are present in each atom. For example, the calcium atom in calcium chloride, CaCl2, has two valence electrons, and the chlorine atoms have seven valence electrons each.
Answer: The correct option is A.
Explanation: In a chemical reaction, reactants react to form a number of products.
For the formation of products, the bonds of the individual reactants must be broken and the bonds of the products must be formed.
For example: Formation of water from hydrogen gas and oxygen gas. Reaction follows:

The Bonds of hydrogen and oxygen molecule are broken and new bonds between hydrogen and oxygen atoms are formed to give water molecule.
From what I can recall, I believe the answer is pantothenic acid; acyl transfer. I'm a bio major, hope I helped. :)
Characteristics of a Precipitate:
A precipitate is characterized by the following properties:
Appears as a solid species.
Settled down at the bottom of the reaction pot.
Insoluble in the corresponding solvent.