Which of the classifications for humans means that we have a hollow nerve chord?
a) class
b) kingdom
c) order
d) phylum

Phylum  

Explanation:

A notochord can be defined as the beginning to the backbone which is primitive. It appears in the embryos as a flexible rod which is made from the germ layer called as mesoderm.

It is one of the 3 layers that is found in the body. These layers are ectoderm, endoderm and mesoderm.

Notochords are only found in the phylum chordata. This phylum belongs a group of animals which includes human.

answer is: c. the experiment shows that the red substance experienced a chemical change.

this is chemical change (chemical reaction), because two new substances are formed (metalig liquid and gas), the atoms are rearranged and the reaction is followed by an energy change.

this is example of chemical decomposition.

chemical decomposition (analysis) is the separation of a single chemical compound into its two or more elemental parts or to simpler compounds.  

chemical decomposition is opposite of chemical synthesis.

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.