The density of an object with a volume of 5.0ml and a mass of 20.0g is
15.0g/ml
0.25g/ml
100.0g/ml
4.0g/ml

The density of the object will be 4 g/ml.

Explanation:

Density is defined as the mass contained per unit volume.

Given : Mass of object = 20.0 grams

Volume of object=

Putting in the values we get:

Thus density of the object will be 4 g/ml.

b) mutualism

hope this : )

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.