which one of the following is a physical change?
a. in cold weather, water condenses on the inside surface of single pane windows.
b. grape juice left in an open unrefrigerated container turns sour.
c. when ignited with a match in open air, paper burns
d. when heated strongly, sugar turns dark brown.
e. when treated with bleach, some dyed fabrics change color.

i believe the answer is c. "baking" is the gerund, while "baking blueberry muffins" would be the gerund phrase. hope this ! : )

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.