Logic of a solution: *Carbon monoxide is a gas produced by furnaces and other devices that burn fuel. Cabins have wood burning stoves and propane furnaces. Carbon monoxide is a gas produced by burning propane.*
*(D)*
The original question: *What gas is produced by burning propane?
Options:
- (A) Greenhouse gases
- (B) Sulfur dioxide
- (C) gasoline
- (D) Carbon monoxide
- (E) hydrocarbons
- (F) carbon dioxide
- (G) dangerous
- (H) heating liquids*

Line 1: *Flatworms belong to the phylum Platyhelminthes. Most of the flatworms are parasitic, although the Turbellaria are free-living in fresh water. Phylum Platyhelminthes are mostly parasitic.*
*(E)*
Line 2: *Phylum platyhelminthes are mostly what?
Options:
- (A) animals
- (B) engorged
- (C) fungi
- (D) infected
- (E) parasitic
- (F) insects
- (G) huge
- (H) free living*

Logic of a solution: *Mammals have a layer of fat under the skin to help insulate the body. If it has hair it is a mammal. An organism with hair has a layer of fat under the skin to help insulate the body.*
*(A)*
The original question: *What does a hairy organism have under its skin to help insulate the body?
Options:
- (A) fat
- (B) hair
- (C) food
- (D) cell
- (E) nerves
- (F) coat
- (G) fur
- (H) marrow*

Line 1: *Arteries generally carry oxygen-rich blood. Arteries carry blood away from our heart. Oxygen-rich blood is carried away from our heart.*
*(F)*
Line 2: *Oxygen-rich blood is carried where?
Options:
- (A) it keeps an organism warm
- (B) mouth of rivers
- (C) The area was once underwater
- (D) running and lifting
- (E) the body's largest organ
- (F) away from the heart
- (G) Earth orbiting the Sun
- (H) four limbs*

Logic of a solution: *Mammals have a layer of fat under the skin to help insulate the body. All humans are mammals. Humans have a layer of fat under the skin to help insulate the body.*
*(E)*
The original question: *What has a layer of fat under the skin to help insulate the body?
Options:
- (A) goats
- (B) snakes
- (C) hamburgers
- (D) animals
- (E) humans
- (F) rabbit
- (G) bears
- (H) fur*

Logic of a solution: *Energy is passed up a food chain or web from lower to higher trophic levels. Energy and carbon in organic compounds passed through food chain to herbivores and carnivores. Carbon in organic compounds are passed through the food web from herbivores to carnivores.*
*(E)*
The original question:
*Carbon in organic compounds are passed through the food web from what?
Options:
- (A) it helps plants in growing
- (B) Burning fuel and air
- (C) members of their own species
- (D) people to dogs
- (E) herbivores to carnivores
- (F) carnivores to plants
- (G) passenger pigeons
- (H) predators to prey*