Why do you think Vera and Domingo ended up with three substances after the chemical reaction while Lee only ended up with two?

the answer to your question is c.

if you read the house of usher you should know that the house was haunted

a compound is a molecule made of atoms from different elements.

a. by the combination of an unlimited number of elements

a gas, having a molecular weight of 13 kg/kmol and a kinematic viscosity of 0.25 cm2/s, flows through a pipe 0.25 m internal diameter and 5 km long at the rate of 0.4 m3/s and is delivered at atmospheric pressure.