[Q] _ are an essential nutrient for animals.
Options:
- (A) Energy
- (B) Chemicals
- (C) trees
- (D) potatoes
- (E) Acids
- (F) allow growth
- (G) store
- (H) Proteins
[A] Here's my solution: All animals are heterotrophs. Proteins are an essential nutrient for heterotrophs . Proteins are an essential nutrient for animals. The answer is (H).

[Q] Where does intense activity occur in a plant?
Options:
- (A) Roots
- (B) Buds
- (C) bamboo
- (D) fields
- (E) Summer
- (F) years
- (G) Hairs
- (H) Petals
[A] Here's my solution: Roots have primary and secondary meristems for growth in length and width. Meristems are zones of intense activity. Roots are zones of intense activity. The answer is (A).

[Q] What obtain their food from plants and cannot make their own food?
Options:
- (A) bacteria
- (B) Flowers
- (C) trees
- (D) lichen
- (E) animals
- (F) fungi
- (G) humans
- (H) grass
[A] Here's my solution: Heterotrophs are living things that cannot make their own food. All animals are heterotrophic and obtain their food from plants. Animals obtain their food from plants and cannot make their own food. The answer is (E).

[Q] What do organisms in the lowest trophic level use as food?
Options:
- (A) Organic compounds
- (B) food and shelter
- (C) heat energy
- (D) Chemical energy
- (E) Chlorophyll
- (F) members of their own species
- (G) scarce resources
- (H) inorganic molecules
[A]
Here's my solution: Producers make food from inorganic molecules. Primary producers make up the lowest trophic level. The lowest trophic level makes food from inorganic molecules. The answer is (H).